Ok, sorry ^^
Basically, you have to revert the value of an output pin when the pin is connected to the ground of the component. This is called "sinking" instead of "sourcing", which is when you output power to the component.
You often sink current from components instead of sourcing them because the µC can sink more than it can source, since sinking just basically means "connecting to GND"
So, if a component is connected on the gnd side on a pin, and on the cathode side on a power source, you just reverse the values you send : Putting the pin to 0 or LOW will sink 100% of the power (within the limit of the µC capabilities, of course.), putting it to HIGH or PWM255 will prevent electricity to circulate.
I hope I made myself clear... I'm not sure 