Algorithm to convert any positive integer to an RGB value

Question

We have a heatmap we want to display. The numbers that will make up the values being displayed are unknown (except that they will be positive integers). The range of numbers

Answer 1

Function for colorbar

// value between 0 and 1 (percent)   
function color(value) {
    var RGB = {R:0,G:0,B:0};

    // y = mx + b
    // m = 4
    // x = value
    // y = RGB._
    if (0 <= value && value <= 1/8) {
        RGB.R = 0;
        RGB.G = 0;
        RGB.B = 4*value + .5; // .5 - 1 // b = 1/2
    } else if (1/8 < value && value <= 3/8) {
        RGB.R = 0;
        RGB.G = 4*value - .5; // 0 - 1 // b = - 1/2
        RGB.B = 1; // small fix
    } else if (3/8 < value && value <= 5/8) {
        RGB.R = 4*value - 1.5; // 0 - 1 // b = - 3/2
        RGB.G = 1;
        RGB.B = -4*value + 2.5; // 1 - 0 // b = 5/2
    } else if (5/8 < value && value <= 7/8) {
        RGB.R = 1;
        RGB.G = -4*value + 3.5; // 1 - 0 // b = 7/2
        RGB.B = 0;
    } else if (7/8 < value && value <= 1) {
        RGB.R = -4*value + 4.5; // 1 - .5 // b = 9/2
        RGB.G = 0;
        RGB.B = 0;
    } else {    // should never happen - value > 1
        RGB.R = .5;
        RGB.G = 0;
        RGB.B = 0;
    }

    // scale for hex conversion
    RGB.R *= 15;
    RGB.G *= 15;
    RGB.B *= 15;

    return Math.round(RGB.R).toString(16)+''+Math.round(RGB.G).toString(16)+''+Math.round(RGB.B).toString(16);
}