You talk to her and engage in her in fun, simple activities. Walk around the room with her and point objects out, also fun to do this at the store, outside... It will also help her in language development.
"Look at this blue ball, see how it is round like a circle? Look, your shirt is also blue!"
"Here are three cheese slices. One, two, three. They are yellow and shaped like a square! What else is yellow?" then show her something yellow.
Also, read to her those board boards, there are tons of books her age that introduce colors, shapes, numbers, letters. You don't have to worry about 'teaching' her formally or using flashcards or anything, babies and toddlers learn through play.
Have you joined http://www.BabyCenter.com ? It's free and it you put your child's date of birth in when you sign up, it will give you lots of weekly and monthly advice for her age. I also recommend the "What to Expect the 1st Year/Toddler Year" books.