Check what the codes permit, according to your own Local Authority Having Jurisdiction. (Generally, start with your town and work upward, since the most local rule is the one which you have to satisfy.) In many areas, fuse/breaker boxes must be exposed so you can get to them quickly in an emergency. In other areas you can build a closet around them but no smaller container. In other areas... Paint is the only answer that's likely to be acceptable almost everywhere. And I wouldn't be surprised if some inspector, somewhere, set down rules about what colors you could paint it. The web can only give you generalities when it comes to building codes and the like. You really do have to do some local homework.