Most car fuses are either blue or red, but a 40 amp fuse could be any color. The colors of automotive fuses are not always standardized, so it's best to consult your car's owner's manual to be sure. That said, most 40 amp fuses will be a different color than lower-amp fuses in order to easily distinguish them. So, if you're looking for a 40 amp fuse in your car, it's likely to be a different color than the other fuses in the fuse box.