RGB LED common cathode with 3.3V GPIO +single transistor
The temptation is to invert the circuit but this will fail.



Figure 1. The protection diodes on most logic chips creates a sneak-path to positive supply. This will keep the PNP transistor permanently turned on and may damage the chip. Source: High-side fail.

You need to add a second transistor.



Figure 2. To drive a high-side transistor from a GPIO pin we need a level translator. An NPN transistor does the job nicely.

There is a little more information in my article in the link.