I've seen some tuts that explain that I have to set the colour with analogWrite([i]colour[/i], 0 if I have to turn off that colour and vice versa.
So that seemed a strange behavior. To avoid errors, I post the image of my led here (it's attached!)
If the LED is common anode ( impossible to tell from the photo) then the analogWrite sinks current, so the action of analogWrite is inverted - 0 turns the LED on full, and 255 turns it off.
If you want to write, say, 25/255 brightness, and a variable "brightness" contains 25, then analogWrite (redPin, 255 - brightness);