I can color shift through the rainbow on panels with a formula. But getting a bmap from the screen and putting onto a panel takes a long time and the colorshifting one is also fairly slow. If you're wandering how to shift hue (colors through the rainbow) with a single number, colorvar going from 0 to 360 in this example, here's the formula:
my.red=125+fcos(colorvar,125);
my.green=125+fcos(colorvar-120,125);
my.blue=125+fcos(colorvar-240,125);
as you can see, the green and blue are simply shifted to the right 120 and 240 degrees making each of the colors equally spaced out for a smooth rainbow transition. You can probably do this with the gamma ramp dll posted by Lion_ts recently.