tights over the rear lights is a bit tacky though.
instead of using tint spray, which also looks tacky, why dont you colour code them? Go to a decent spray shop, get them to mix you up a very weak mixture of your body colour and paint it on very thinly.
Done properly, the lights will still shine through ok. If you dont want bodycoloured, you could spray them any other colour.
Or alternatively, a cheap way of doing it is to buy red tint spray rather than black, easily available from halfords.