I sprained my ankle over 4 years ago and it is still bruised like it was, is it normal?

No. Bruising is for 4 years is not normal, however it is possible what you are seeing is not bruising. There is a muscle on the top of the foot that can appear dark if you have fair skin and can look like a bruise. If you have pain associated with the bruising I recommend you see a podiatrist for evaluation and xrays. They may also want to get an MRI.