Take the above color wheel. Color families, would be colors that are next to each other on the wheel. Complimentary colors are opposite to each other on the wheel. There are a few ways to do color blocking. You can start very basic, with a bright color and a neutral.
You can also color block with two colors. Either monochromatically or color families such as pink and red or violet and pink. Or also, complimentary colors such as orange and blue.
If you want to do three colors stick to two in a color family and one compliment. Or three compliments.
Overall, just have fun! Remember accessories are key! If you're wearing color from head to toe, keep accessories neutral. Try to keep a good balance. Color blocking is easy to do with what you have in your closet, but if you want to go out and buy new pieces just have fun with it, be bold and go bright! You can't really go too wrong unless you're wearing Christmas colors.