Connecting KY-009 to GPIO of Raspberry Pi
Why not save yourself some trouble and use an RGB LED driver?  You could connect multiple ones to your I2C port or even bitbang over gpio.  Something like the LP3944 or the LP5521

The LP3994 has eight channels and handles the current control for you.  You can even DIM over I2C.  They make a wide variety of these things, some with integrated boosters, controllers, etc.