Hey, I'm on mobile so didn't check any linked resources, but it sounds like you are trying to put the LEDs in series. The typical voltage drop on a LED is between 1.7 and 3.3 V depending on the colour, so it's normal that you cannot put more than a few LEDs in series on 5 V.
The LEDs need to be wired in parallel, each with its resistor. They need to be switched on/of using a MOSFET as they will consume a few hundred mA depending on the desired brightness.
RGB diodes are essentially 3 diodes in one package - red, green and blue. You would need to control the brightness of each colour independently to get the desired colour.
If I were you I would use RGB modules with a built-in driver, like WS2812B. They only need one data pin that allows sending serial data to each module and set its colour/brightness independently.
Hope that helps at least a bit