> I would like to experiment with a 3 color LED to see what colors
> it can make.
> The commercial color LED drivers seem targeted for cell phones
> and are extremely small surface mount parts making them difficult
> to work with.

You can get free samples, must be worth a look and some effort

http://www.marktechopto.com/index.cfm?a=135

> I would like to have good control of the current in the Red, Blue
> and Green LEDs.  The forward drops for the 3 colors are
> considerably different with Blue a little over 3.5 Volts.  This is a
> problem in that a small change in the supply voltage or LED
> temperature will cause a big change in the LED current is simple
> dropping resistors are used from a +5 Volt rail.

Why are you worried about the 5V dropping ? I don't actually
see a good reason why a well-regulated supply would, not
at the sort of current levels that LEDs need if it's got suitable
current and filtering

What temperature rise are you expecting ? LEDs change peak f
by only a dozen nm when T goes from ambient to ambient +100C,
and that's really starting to cook them. Similarly with current. If they're
getting hot enough to be a concern you're probably damaging them,
and the LED god is going to be most displeased

> One approach would be to use 3 independent current sources,
> each good for 100 ma and switch them on and off (PWM) with
> an 8 pin PIC

A simple way would be with an LM317 and a resistor

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