So you are suggesting me to use each (3) PWM output for one color and put a transistor on each color line to guarantee the needed current, right?With this solution i will not have any problem, but all sides will have the same color. Right?
Yes all the sides will be the same colour but with only three PWM outputs you don't have a choice unless you use some other chip to generate the PWM signal for you. Other options are to go for LED drivers, I like the PCA9685 chip, that is I2C controlled and gives 16 PWM outputs so you need just the one chip to do what you want with a different colour on each side. It will drive up to 25mA per output.