Accidentally hit a button, everything turned blue-purple?

Hello-- I am new to AE and working on a motion graphics project. I was sort of doing two things at once and accidentally hit a button or something that turned everything in my entire animation a shade of blue and purple. I am working with objects I created in AI and imported to AE. When I ctrl+z it will go back through the steps I've done but the colors stay blue-ish, so I assume I have activated some sort of mask or something (like in Ps when you hit mask and everything turns red) but I can't figure out how to make it go back! Any help is much appreciated.

Thanks,
Emily