The color is actually red. The flash of red indicates the moment AF locked onto your subject. The points that flash are the AF points that achieved a focus lock. With the 7D, this only happens in single-shot AF mode, but it IS normal behavior. If you have one of the viewfinder grid displays on, the whole grid will also flash.

I believe it is possible to enable this functionality to only occur under darker circumstances. When the bulk of the frame is dark (below 18% gray, as read by the meter), then usually the red flashing will occur. This is because the viewfinder uses a transmissive LCD, which makes the black AF points semi-translucent. They can easily disappear into a dark scene, making them impossible to see. They flash to give you a moment to see what is actually in focus under those circumstances.

If you switch to AI Servo mode, the flashing will no longer occur. Some people love this, however others who use AI Servo exclusively (such as myself) have found it to be an often frustrating feature...even though I may use continuous AF drive, it is still helpful to know periodically which AF points lock on (beyond just the focus confirmation dot...which doesn't actually tell you anything about which AF points actually acquired focus.) In single-point mode, this doesn't matter much...the AF confirm dot does the job. In any multi-point mode (which, with the 7D, you have several...expanded, zone, and all points), flashing red would be useful (and is rumored to be coming in a future firmware update.)

If you do NOT like this feature, you can disable it with the menus. Sadly, my 7D is off for repair and calibration, so I cant go digging through the menus to tell you exactly which one. It is either the custom function menus, or one of the red or yellow menus.