The results of my experimenting with my rear lights:

As you can see, all I've really managed to achieve is to make them a little darker with an odd matte finish, and that's after 2 cans of tinting spray and 2 thirds of a can of lacquer. They look.... ok. I guess. As long as you don't look too closely.
Really tempted to just take them back off and hand them over to the paint guru at work (who's already offered to help me with them), I'm very obviously no good at this sort of thing
. Or I can leave them on for Combe so you can all point and laugh 

As you can see, all I've really managed to achieve is to make them a little darker with an odd matte finish, and that's after 2 cans of tinting spray and 2 thirds of a can of lacquer. They look.... ok. I guess. As long as you don't look too closely.
Really tempted to just take them back off and hand them over to the paint guru at work (who's already offered to help me with them), I'm very obviously no good at this sort of thing