@Trent3 Do you wanna build all of them? And how long should the maximum strip be?
There are many ways how to do it, but as I wrote before, not really any easy ones. For very short strip (less than 20cm), its ok to use linear drivers (current mode is best since they react on voltage from cca 7V to 13V and each collor respond differently to voltage, but +- same to current).
My suggestions:
1.
http://www.elektrodilna.wz.cz/data/majak/majak-schema.jpg will do the changing of collors, but it won't really make much shading. But I can't think of anything more simple and you could use this schematic directly (as the common pin is usually +12V).
2. You could use simple logic components. The biggest problem will be swapping to next chanel, ofc. if you don't wanna make everything three times... I made some drawing, it's not really great but I don't have time to make it any better
So first idea is to take 4b counter. You could use it to generate kind of ramp signal. Four resistor at the output are actually I/U converter. As it counts up, there is more current going through R, 2R and 4R. This makes more voltage at the input of the MUX. Driver would be U/I converter, or you could use some U/PWM converter (with digital mux). The other counter is just for switching the collors.
3. You could use simple triangle generator. Fast one generates base for PWM, slow one makes the shading of signal (they should have time constants like <1Hz slow and 1kHz fast). You will need something to swich chanels, square output (f.e. falling edge) from slow one should give you the signal when to change.
4. The same thing could as 2. could be done with shift registors. The difference is that you get less shades (just 4 different stages). Transistors at the upper right corner (i draw bipolar, but they should be unipolar) generates first 1 stage, that is then shifted. through.
5. You could make ramp generators from three 555. Transistors with diode make current source that is charging cap. You could probably use falling edge of that ramp signal to swich another 555 (you may have to add another resistor from each 2 pin of 555 to ground). output can again go to pwm generator (simpliest is to use triangle gen. like in 3. and three comparators) or use linear current sorce as i draw.
I don't have time to build any of these so there will be some debuging, but I think that those concepts could work.