I have a 2 year old filly. She eats and pes stool and urine normally. But drinks alot. Is this colic?

Nope, not colic. While there are a few types of colic(not always impaction) I don't know of a "too much pee" symptom. Anyway, is she on a high protein diet? Too much protein can cause kidney problems, which could show extreme thirst( and darker, more concentrated urine). She could also be coming into heat. If she seems normal, she probably is! She may be jut bored, or like the salt and therefore thirsty.