You are probably rather proud of your long, blonde hair, like to show off your perfectly shaved, bald head, or enjoy keeping your hair short, so it feels comfortable during the summer months when you sport a baseball cap. Regardless of your hair (or lack of hair), you are not always going to match the hair of a particular character you are looking to dress up like. Even if you have the same hair length but the wrong color, you have two different options: dye your hair or purchase a wig. It is going to be far easier than cutting/growing your hair and dying it. Besides, if you find you look good with the brown or brunette wigs, you are more than welcome to grow out and dye your hair to the same color later on down the road anyways. It is just easier to purchase them now.
There are so many different wigs out there, it is possible to match any hairstyle you want for your costume. Brown and brunette wigs allow you to complete any particular look that you might want to go with. If you just want a stylish brown style to make you look like a 1970s singer, or you want a chopped brunette look that matches your favorite movie character, there is always going to be something that matches your particular look. Just make sure to search through all of the options, as there are going to be so many to choose from.