I've used these clips before and it never happened. Now when I click on a clip to select it in its track, it looks normal, and when I click play it goes darker. Then I can re-click it and it goes light, and when I click to play again, it goes darker again. It's not on all the clips, just two of them and only when placed in Track 3 and 4. What is happening?

I am new at this. Please help!