Till Clive pops up, I'll try n answer this
On the headlights its a complete no no cause it isn't worth risking getting pulled by the black rats. As if they don't like it and you can't remove it at the roadside (if it's sprayed on for example) then your car will me taken off the road till it's ok'd by vosa
If you want black headlights, you'll want new head light units that have black inners instead, or other coloured inners for that matter.
You could always give opening your current light units a go by sticking em in the oven on a low temperature for a few minutes to break down the adhesive, prize em open n spray the inners before resealing em. Sounds mad but a fair few members have done this themselves. just be careful not to bake em too much or they'll just melt. This could obviously be quite risky though n you may suffer from condensation inside the light units if not re-sealed well enough after. A silica bag could solve this though.
Another option is fly eye film or spi vision, its a perforated vinyl that you stick to the exterior of the light units. From a distance the head lights will look tinted and will allow light to shine through. but up close it just looks like you've wrapped a pair of tights round em. It is also available in different colours if you was to want red so this may be an option for you.
But the problems with fly eye is that its nowhere near as easy to apply as they make out, it can crease like mad n if you heat it up too much it will melt. it is horrible sticky stuff to work with. Also, it does cut out a fair bit of light output, a lot more than they say it does.
I used to have fly eye fitted to my headlights n tail lights, I use osram cool blue intense bulbs, which normally are very bright n light up unlit country roads beautifully, but with fly eye fitted the light beam from the osrams was quite dull, almost as bad as standard yellow bulbs.
For this reason, solid tint films are a definite no no as you'll almost definitely get pulled n be told to remove it, even if sellers on ebay do claim its road legal cause it'll cut out even more light than fly eye. The fly eye though you can get away with on the headlights.
With the tail lights you can get away with a bit more, but if getting the lights tinted i'd recommend getting them done professionally cause if you spray em yourself you may end up going to dark.
Or you could use fly eye also, but I recently removed the fly eye from my tail lights cause it doesn't weather as well as they make out, and there was a few patches where it had broke off so it didn't look very good n i ended up removing it completely. This brings me onto it being horrible sticky stuff to remove, as it isn't reusable as they claim, so instead of pealing it back off in one neat sheet, it'll tear off in many tiny bits.
One very good thing I can say about it though, is my motor sailed through it's MOT beautifully with not one advisory. Even though the bloke who did my MOT said how much he didn't like it, he couldn't not pass it as enough light shined through.
So because of this, fly eye may be a decent cheap option for you at least temporary anyway n if you take your time you can get a good result with it.
I have now since purchased some projector headlights with black inners, they look so much better and are very bright. I've also got my eyes on some LED aftermarket black tail light units.
I've still got fly eye fitted to my reverse lights n at some point i'll fly eye my front fog lights as i never use em anyway n they'll make the front end look more stealthy looking black.
This is what my motor looked like with the factory chrome units fitted
This is them with fly eye fitted
This is the light emitted with fly eye fitted
Reversed lights fly eyed
Light emitted with fly eye fitted
These are my new black projector headlights
This is the light emitted from the new lights
You can see the difference in brightness between the 2 lots of light beams
Oh and the new units also have built in DRL's in the form of halo's :P
Really long post for you but hopefully you'll find it informative