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

Simple algorithm

// given a max and min value
float red,green,blue;
float range=max-min;
float mid=(max+min)/2.0;

//foreach value
    red = (value[ii]-mid)/range;            
    if (red>0.0) {
        //above mid = red-green
        blue=0.0;
        green = 1.0-red;
    } else {
        // lower half green-blue
        blue=-red;
        green = 1.0-blue;
        red=0.0;
    }

}

More complex:
If your range is a few million but most are around 0 you want to scale it so that 'red' in the above example is the log of the distance from the midpoint. The cod eis a little more complicated if the values are +/-

// assume equally distributed around 0 so max is the largest (or most negative number)
float range = log(fabs(max));
float mid=0.0

// foreach value
if (value[ii] > 0.0 ) {
    // above mid = red-green
    red = log(value[ii])/range;
    blue=0.0;
    green = 1.0 - red;
} else {
    // below mid = green-blue
    blue=-log(value[ii])/range;
    green = 1.0 - blue;
   red = 0.0;
}

note - I haven't tested this code, just spinning ideas!