Happy Hues – Curated colors in context via https://news.ycombinator.com/item?id=21780659 which links to awesome article https://refactoringui.com/previews/building-your-color-palette/ (which talks about why other color scheme sites are lame; 5 colors is too few) as well as this open source scheme among other links.
Source unknown. Original note is "Returns either black or white only. 'YIQ' color space used."
// php version
function getContrastYIQ($hexcolor){
$r = hexdec(substr($hexcolor,0,2));
$g = hexdec(substr($hexcolor,2,2));
$b = hexdec(substr($hexcolor,4,2));
$yiq = (($r*299)+($g*587)+($b*114))/1000;
return ($yiq >= 128) ? 'black' : 'white';
}
// javascript version
function getContrastYIQ(hexcolor){
var r = parseInt(hexcolor.substr(0,2),16);
var g = parseInt(hexcolor.substr(2,2),16);
var b = parseInt(hexcolor.substr(4,2),16);
var yiq = ((r*299)+(g*587)+(b*114))/1000;
return (yiq >= 128) ? 'black' : 'white';
Guessing intent was to suggest whether to show a color against black or white…?
NOTE the following was originally all written on one line. It broke lokidb indexing.
lutTurbo = [
[0.18995,0.07176,0.23217],
[0.19483,0.08339,0.26149],
[0.19956,0.09498,0.29024],
[0.20415,0.10652,0.31844],
[0.20860,0.11802,0.34607],
[0.21291,0.12947,0.37314],
[0.21708,0.14087,0.39964],
[0.22111,0.15223,0.42558],
[0.22500,0.16354,0.45096],
[0.22875,0.17481,0.47578],
[0.23236,0.18603,0.50004],
[0.23582,0.19720,0.52373],
[0.23915,0.20833,0.54686],
[0.24234,0.21941,0.56942],
[0.24539,0.23044,0.59142],
[0.24830,0.24143,0.61286],
[0.25107,0.25237,0.63374],
[0.25369,0.26327,0.65406],
[0.25618,0.27412,0.67381],
[0.25853,0.28492,0.69300],
[0.26074,0.29568,0.71162],
[0.26280,0.30639,0.72968],
[0.26473,0.31706,0.74718],
[0.26652,0.32768,0.76412],
[0.26816,0.33825,0.78050],
[0.26967,0.34878,0.79631],
[0.27103,0.35926,0.81156],
[0.27226,0.36970,0.82624],
[0.27334,0.38008,0.84037],
[0.27429,0.39043,0.85393],
[0.27509,0.40072,0.86692],
[0.27576,0.41097,0.87936],
[0.27628,0.42118,0.89123],
[0.27667,0.43134,0.90254],
[0.27691,0.44145,0.91328],
[0.27701,0.45152,0.92347],
[0.27698,0.46153,0.93309],
[0.27680,0.47151,0.94214],
[0.27648,0.48144,0.95064],
[0.27603,0.49132,0.95857],
[0.27543,0.50115,0.96594],
[0.27469,0.51094,0.97275],
[0.27381,0.52069,0.97899],
[0.27273,0.53040,0.98461],
[0.27106,0.54015,0.98930],
[0.26878,0.54995,0.99303],
[0.26592,0.55979,0.99583],
[0.26252,0.56967,0.99773],
[0.25862,0.57958,0.99876],
[0.25425,0.58950,0.99896],
[0.24946,0.59943,0.99835],
[0.24427,0.60937,0.99697],
[0.23874,0.61931,0.99485],
[0.23288,0.62923,0.99202],
[0.22676,0.63913,0.98851],
[0.22039,0.64901,0.98436],
[0.21382,0.65886,0.97959],
[0.20708,0.66866,0.97423],
[0.20021,0.67842,0.96833],
[0.19326,0.68812,0.96190],
[0.18625,0.69775,0.95498],
[0.17923,0.70732,0.94761],
[0.17223,0.71680,0.93981],
[0.16529,0.72620,0.93161],
[0.15844,0.73551,0.92305],
[0.15173,0.74472,0.91416],
[0.14519,0.75381,0.90496],
[0.13886,0.76279,0.89550],
[0.13278,0.77165,0.88580],
[0.12698,0.78037,0.87590],
[0.12151,0.78896,0.86581],
[0.11639,0.79740,0.85559],
[0.11167,0.80569,0.84525],
[0.10738,0.81381,0.83484],
[0.10357,0.82177,0.82437],
[0.10026,0.82955,0.81389],
[0.09750,0.83714,0.80342],
[0.09532,0.84455,0.79299],
[0.09377,0.85175,0.78264],
[0.09287,0.85875,0.77240],
[0.09267,0.86554,0.76230],
[0.09320,0.87211,0.75237],
[0.09451,0.87844,0.74265],
[0.09662,0.88454,0.73316],
[0.09958,0.89040,0.72393],
[0.10342,0.89600,0.71500],
[0.10815,0.90142,0.70599],
[0.11374,0.90673,0.69651],
[0.12014,0.91193,0.68660],
[0.12733,0.91701,0.67627],
[0.13526,0.92197,0.66556],
[0.14391,0.92680,0.65448],
[0.15323,0.93151,0.64308],
[0.16319,0.93609,0.63137],
[0.17377,0.94053,0.61938],
[0.18491,0.94484,0.60713],
[0.19659,0.94901,0.59466],
[0.20877,0.95304,0.58199],
[0.22142,0.95692,0.56914],
[0.23449,0.96065,0.55614],
[0.24797,0.96423,0.54303],
[0.26180,0.96765,0.52981],
[0.27597,0.97092,0.51653],
[0.29042,0.97403,0.50321],
[0.30513,0.97697,0.48987],
[0.32006,0.97974,0.47654],
[0.33517,0.98234,0.46325],
[0.35043,0.98477,0.45002],
[0.36581,0.98702,0.43688],
[0.38127,0.98909,0.42386],
[0.39678,0.99098,0.41098],
[0.41229,0.99268,0.39826],
[0.42778,0.99419,0.38575],
[0.44321,0.99551,0.37345],
[0.45854,0.99663,0.36140],
[0.47375,0.99755,0.34963],
[0.48879,0.99828,0.33816],
[0.50362,0.99879,0.32701],
[0.51822,0.99910,0.31622],
[0.53255,0.99919,0.30581],
[0.54658,0.99907,0.29581],
[0.56026,0.99873,0.28623],
[0.57357,0.99817,0.27712],
[0.58646,0.99739,0.26849],
[0.59891,0.99638,0.26038],
[0.61088,0.99514,0.25280],
[0.62233,0.99366,0.24579],
[0.63323,0.99195,0.23937],
[0.64362,0.98999,0.23356],
[0.65394,0.98775,0.22835],
[0.66428,0.98524,0.22370],
[0.67462,0.98246,0.21960],
[0.68494,0.97941,0.21602],
[0.69525,0.97610,0.21294],
[0.70553,0.97255,0.21032],
[0.71577,0.96875,0.20815],
[0.72596,0.96470,0.20640],
[0.73610,0.96043,0.20504],
[0.74617,0.95593,0.20406],
[0.75617,0.95121,0.20343],
[0.76608,0.94627,0.20311],
[0.77591,0.94113,0.20310],
[0.78563,0.93579,0.20336],
[0.79524,0.93025,0.20386],
[0.80473,0.92452,0.20459],
[0.81410,0.91861,0.20552],
[0.82333,0.91253,0.20663],
[0.83241,0.90627,0.20788],
[0.84133,0.89986,0.20926],
[0.85010,0.89328,0.21074],
[0.85868,0.88655,0.21230],
[0.86709,0.87968,0.21391],
[0.87530,0.87267,0.21555],
[0.88331,0.86553,0.21719],
[0.89112,0.85826,0.21880],
[0.89870,0.85087,0.22038],
[0.90605,0.84337,0.22188],
[0.91317,0.83576,0.22328],
[0.92004,0.82806,0.22456],
[0.92666,0.82025,0.22570],
[0.93301,0.81236,0.22667],
[0.93909,0.80439,0.22744],
[0.94489,0.79634,0.22800],
[0.95039,0.78823,0.22831],
[0.95560,0.78005,0.22836],
[0.96049,0.77181,0.22811],
[0.96507,0.76352,0.22754],
[0.96931,0.75519,0.22663],
[0.97323,0.74682,0.22536],
[0.97679,0.73842,0.22369],
[0.98000,0.73000,0.22161],
[0.98289,0.72140,0.21918],
[0.98549,0.71250,0.21650],
[0.98781,0.70330,0.21358],
[0.98986,0.69382,0.21043],
[0.99163,0.68408,0.20706],
[0.99314,0.67408,0.20348],
[0.99438,0.66386,0.19971],
[0.99535,0.65341,0.19577],
[0.99607,0.64277,0.19165],
[0.99654,0.63193,0.18738],
[0.99675,0.62093,0.18297],
[0.99672,0.60977,0.17842],
[0.99644,0.59846,0.17376],
[0.99593,0.58703,0.16899],
[0.99517,0.57549,0.16412],
[0.99419,0.56386,0.15918],
[0.99297,0.55214,0.15417],
[0.99153,0.54036,0.14910],
[0.98987,0.52854,0.14398],
[0.98799,0.51667,0.13883],
[0.98590,0.50479,0.13367],
[0.98360,0.49291,0.12849],
[0.98108,0.48104,0.12332],
[0.97837,0.46920,0.11817],
[0.97545,0.45740,0.11305],
[0.97234,0.44565,0.10797],
[0.96904,0.43399,0.10294],
[0.96555,0.42241,0.09798],
[0.96187,0.41093,0.09310],
[0.95801,0.39958,0.08831],
[0.95398,0.38836,0.08362],
[0.94977,0.37729,0.07905],
[0.94538,0.36638,0.07461],
[0.94084,0.35566,0.07031],
[0.93612,0.34513,0.06616],
[0.93125,0.33482,0.06218],
[0.92623,0.32473,0.05837],
[0.92105,0.31489,0.05475],
[0.91572,0.30530,0.05134],
[0.91024,0.29599,0.04814],
[0.90463,0.28696,0.04516],
[0.89888,0.27824,0.04243],
[0.89298,0.26981,0.03993],
[0.88691,0.26152,0.03753],
[0.88066,0.25334,0.03521],
[0.87422,0.24526,0.03297],
[0.86760,0.23730,0.03082],
[0.86079,0.22945,0.02875],
[0.85380,0.22170,0.02677],
[0.84662,0.21407,0.02487],
[0.83926,0.20654,0.02305],
[0.83172,0.19912,0.02131],
[0.82399,0.19182,0.01966],
[0.81608,0.18462,0.01809],
[0.80799,0.17753,0.01660],
[0.79971,0.17055,0.01520],
[0.79125,0.16368,0.01387],
[0.78260,0.15693,0.01264],
[0.77377,0.15028,0.01148],
[0.76476,0.14374,0.01041],
[0.75556,0.13731,0.00942],
[0.74617,0.13098,0.00851],
[0.73661,0.12477,0.00769],
[0.72686,0.11867,0.00695],
[0.71692,0.11268,0.00629],
[0.70680,0.10680,0.00571],
[0.69650,0.10102,0.00522],
[0.68602,0.09536,0.00481],
[0.67535,0.08980,0.00449],
[0.66449,0.08436,0.00424],
[0.65345,0.07902,0.00408],
[0.64223,0.07380,0.00401],
[0.63082,0.06868,0.00401],
[0.61923,0.06367,0.00410],
[0.60746,0.05878,0.00427],
[0.59550,0.05399,0.00453],
[0.58336,0.04931,0.00486],
[0.57103,0.04474,0.00529],
[0.55852,0.04028,0.00579],
[0.54583,0.03593,0.00638],
[0.53295,0.03169,0.00705],
[0.51989,0.02756,0.00780],
[0.50664,0.02354,0.00863],
[0.49321,0.01963,0.00955],
[0.47960,0.01583,0.01055]
]
really nice vibrant css color gradient maker - uses non-RGB space