Percentage-wise display of RGB color from red through yellow to green

I am thinking of a nice way of displaying a status in terms of color-coding that is entirely fluid. 

I was thinking to go from red through yellow to green, and maybe I will define blue as the color for an actual 100% "or process step done"

I developed four  global functions for this in total. One to translate hex into numbers, one to translate numbers into hex, one to define a RGB based on percentage and a final one I picked up from other Ninox users and adapted it to define a darkness level so that you can define whether to use white font color or black font color (contrast to background)

The value "perc" is a number between 0 and 100, the value "threshhold" indicates at what percentage the color should be yellow and start shifting to green

function fnconvhex(num : number) do
    "This function takes a number (should be between 0 - 255) and turns it into a 2-digit hex-code (returns string)";
    let hex1 := "0";
    let hex2 := "0";
    let part1 := floor(num / 16);
    if part1 < 10 then
        hex1 := text(part1)
    else
        switch part1 do
        case 10:
            (hex1 := "A")
        case 11:
            (hex1 := "B")
        case 12:
            (hex1 := "C")
        case 13:
            (hex1 := "D")
        case 14:
            (hex1 := "E")
        case 15:
            (hex1 := "F")
        default:
            void
        end
    end;
    let part2 := num - floor(num / 16);
    if part2 < 10 then
        hex2 := text(part2)
    else
        switch part1 do
        case 10:
            (hex2 := "A")
        case 11:
            (hex2 := "B")
        case 12:
            (hex2 := "C")
        case 13:
            (hex2 := "D")
        case 14:
            (hex2 := "E")
        case 15:
            (hex2 := "F")
        default:
            void
        end
    end;
    hex1 + hex2
end;
function fnperccol(perc : number,threshhold : number) do
    "This function takes a percentage value (perc) and returns a 6-digit RGB hex color (#FFFFFF) from red to yellow color until (threshhold) value and then from yellow to green";
    let myvar := 200;
    let myhex := "";
    if perc <= threshhold then
        myvar := round(200 * perc / threshhold);
        myhex := "#F0" + text(fnconvhex(myvar)) + "00"
    else
        myvar := 230 - round((perc - threshhold) / (100 - threshhold) * 200);
        myhex := "#" + text(fnconvhex(myvar)) + "CC00"
    end;
    myhex
end;
function fnhexdarkness(myRGB : text) do
    "This function analyzes a RGB hex-color code and defines a darkness value to determine whether bright or dark font is better";
    let mynum1 := fnhex2num(substr(myRGB, 1, 3));
    let mynum2 := fnhex2num(substr(myRGB, 3, 5));
    let mynum3 := fnhex2num(substr(myRGB, 5, 7));
if  200 - (sqrt(0.299 * pow(mynum1, 2) + 0.587 * pow(mynum2, 2) + 0.114 * pow(mynum3, 2))) < 29 then "#505050" else "white"
end
end