Generally speaking, color blindness seldom occurs to girl. It is more commonly happen to boys. Usually, child with color blindness is particularly slow in learning the difference between yellow and green, red and orange, blue and purple and more colors. And they may also feel difficult to see a white or yellow boundary line painted over grasses.
Since your girl is just three years old, maybe she is not color blind. It is just confused about colors. I hope so. And you should pay more attention, and if it is do, don't worry, there are some way to protect her, there are color blindness corrective mirrors can help her to recognize the color, and you'd better let her wear that when she grows up.
It could be. The color blind means the person who doesn't have the ability to distinguish the difference between three colors that are red, blue and green. If a person couldn't identify one of the three colors, which is called anomalous trichromatic. The most common type is red-green color blind that the person would see red and green as the same color or opposite color. For your child, maybe he/she has color blind, you had better take he/she to know whether there is any eye vision problem or not.