What Sensor?

Hello.

I am intrigued about making a beer pong table. I was wondering if anyone had a suggestion. I know modulated IR Sensors will work for this application but was wanting to see what other options are out there.

THE SITUATION:

Make a beer pong table that has 6 cups on each side. I want two different color LEDs. One color for when there is a cup and another color for when there is not a cup. I want each cup to be able to change color independently. I have already made a table using non-modulated IR as sensors and it works really well inside or in the evening time (outside). The biggest problem I have to overcome is using the table in daylight, while making all the electronics water proof and cost (looking to do this as cheaply as possible but I don't want to half-A$$ it) Any suggestions would be appreciated. Thanks!

RFID's in the cups? magnets in the cups and hall sensors in the table?