tux
create a color envelope (on the bottom right), zoom out the envelope window so you can create a longer envelope and adjust the values more easily. this one is 10 sec long and for the blinking effect the keyframes have a alpha value of 1.00 to 0.300 (1.00 is like 100% brightness and 0.300 is 30%). then assign the envelope to your quad. for more information on how to use the editor and navigate, read the text on the very bottom when hovering over something with your mouse.
I actually have a better suggestion, if you can't read Bezier curves, go to an older version of envelope curves.
