What it will look like when doing what I tried to explain earlier with ASCII graphics - to walk the RGB cube with a space-filling cube where the red channel is walked up/down with highest frequency and blue walked with least frequency. Just as in normal gray code, every single step changes one single color channel one tick up or down.

Larger image here: http://www.8052.com/users/pwm/5x5x5_colors.png

As can be seen, there will still be quite large jumps in the neighbour colors, since the color channels are changed in 25% steps.

Even if increasing the color resolution, an RGB walk will never be a good choice, as has already been mentioned. A color cube will not look good if attempting to walk the colors as one long sequence. This is a similar walk with 9 levels available for each channel - the red will cycle up and down more times when walking from black to white, but the sequence will still not be very pleasant to look at, if used to drive some RGB LEDs. Even if the red channel now doesn't make a huge jump (sawtooth), it cyclic action of the individual color channels will still be very visible. You can change which color channel that represents the "least significant digit", but then you'll just get green or blue to constantly walk up or down. You could even produce a random walk, if you like but while a random walk doesn't show a pattern, it still doesn't produce a pleasing sequence of colors.


The walk sequence for the 5x5x5 RGB cube was:

0 0 0
1 0 0
2 0 0
3 0 0
4 0 0
4 1 0
3 1 0
2 1 0
1 1 0
0 1 0
0 2 0
1 2 0
2 2 0
3 2 0
4 2 0
4 3 0
3 3 0
2 3 0
1 3 0
0 3 0
0 4 0
1 4 0
2 4 0
3 4 0
4 4 0
4 4 1
3 4 1
2 4 1
1 4 1
0 4 1
0 3 1
1 3 1
2 3 1
3 3 1
4 3 1
4 2 1
3 2 1
2 2 1
1 2 1
0 2 1
0 1 1
1 1 1
2 1 1
3 1 1
4 1 1
4 0 1
3 0 1
2 0 1
1 0 1
0 0 1
0 0 2
1 0 2
2 0 2
3 0 2
4 0 2
4 1 2
3 1 2
2 1 2
1 1 2
0 1 2
0 2 2
1 2 2
2 2 2
3 2 2
4 2 2
4 3 2
3 3 2
2 3 2
1 3 2
0 3 2
0 4 2
1 4 2
2 4 2
3 4 2
4 4 2
4 4 3
3 4 3
2 4 3
1 4 3
0 4 3
0 3 3
1 3 3
2 3 3
3 3 3
4 3 3
4 2 3
3 2 3
2 2 3
1 2 3
0 2 3
0 1 3
1 1 3
2 1 3
3 1 3
4 1 3
4 0 3
3 0 3
2 0 3
1 0 3
0 0 3
0 0 4
1 0 4
2 0 4
3 0 4
4 0 4
4 1 4
3 1 4
2 1 4
1 1 4
0 1 4
0 2 4
1 2 4
2 2 4
3 2 4
4 2 4
4 3 4
3 3 4
2 3 4
1 3 4
0 3 4
0 4 4
1 4 4
2 4 4
3 4 4
4 4 4