Question

I would like to come up with as many HEX HTML values to have a smooth color gradient from red to green:

I would like this to be similar to the following:
http://www.utexas.edu/learn/html/colors.html

I don’t have the best eye for color choices, so I’m hoping a standard chart is already put together showing how to transition from red through yellow to green smoothly.

On that website “1 of 6” is most similar to what I’m looking for, but that example is limited to 11 colors:

(1) FF0000 Red, 
(2) FF3300 Red(Orange)
(3) ff6600 
(4) ff9900 
(5) FFCC00 Gold 
(6) FFFF00 Yellow
(7) ccff00
(8) 99ff00
(9) 66ff00
(10) 33ff00
(11) 00FF00 Lime 

It would be great to be able to double the number of colors, but yet make them transition smoothly.

Thanks for any insights and help.

Answer 1

Depending on how many colors you want to end up with, the solution is just to keep incrementing the green value by a certain amount, and then when green is maxed (FF), decrement the red value repeatedly by the same amount.

Pseudo-code:

int red = 255; //i.e. FF
int green = 0;
int stepSize = ?//how many colors do you want?
while(green < 255)
{
    green += stepSize;
    if(green > 255) { green = 255; }
    output(red, green, 0); //assume output is function that takes RGB
}
while(red > 0)
{
    red -= stepSize;
    if(red < 0) { red = 0; }
    output(red, green, 0); //assume output is function that takes RGB
}

Generating by hand, you can simply increment by 16, like so:

FF0000
FF1000
FF2000
FF3000
FF4000
FF5000
FF6000
FF7000
FF8000
FF9000
FFA000
FFB000
FFC000
FFD000
FFE000
FFF000
FFFF00 //max, step by 15
F0FF00 //cheat, start with a -15 to simplify the rest
E0FF00
D0FF00
C0FF00
B0FF00
A0FF00
90FF00
80FF00
70FF00
60FF00
50FF00
40FF00
30FF00
20FF00
10FF00