What's this light

That's your coolant light,your overheating.

I was told at the shop it's a light for the transmission.

OK Makes sense,still a temp. warning light,just for your transmission.

A transmission over heating can cost you a lot of money. It may be slipping which could cause over heating. Did the shop say what is wrong? What does the transmission fluid look like? Brown or Red?

The fluid is red. Shop said it's some kind of sensor needing changes, and it would cost me at least 500 for parts and labor. When the light come on I usually lose power.