Summarize the following:
Once the shrimp are done, they will become firmer in texture. They will also change from gray to a pink salmon color. That's when you know they are done!  The shrimp should be opaque when they're done. They start out a little translucent. Store leftover shrimp in an airtight container in the refrigerator for up to 4 days.

Summary:
Watch for the shrimp to turn a pink color.