What would I have to consider by painting the inside of my headlights black?

Traffic citations?

You'd decrease your visibility to other drivers, be able to out-drive your headlights at a much lower speed (especially on the highways without street lights) and be more of a target than you already are with the illegal front signals you have. Seems generally like a bad idea. What would prompt you to even think about this?

the reflective silver is there for a reason

Well I was just searching on cardomain and some guy painted the inside of his Evo'* black:




And also the Pontiac GTO has that sort of look as well:



I don't know if there'* special paint you need or if there'* a certain way to do it but I really like the look of it and I think it would just be a great subtle change especially for a Bonneville.
And the turn signals I have are a blue bulb but when lit, they're a bright white which, here, is perfectly legal.

Black still tends to absorb light and I believe there would still likely be at least some reduction in forward projection/output. Your original post led me to believe you wanted to paint the inside forward surface (possibly trying to achieve that dark smoked appearance across the entire lens). The inside surfaces of headlamp assemblies are designed to achieve certain results. Changing this may result in enough of a decrease in efficiency to no longer meet FMVSS or CMVSS.

You can see in the photos you posted that the shape of the reflectors is entirely different that in our vehicles. This makes a significant difference.

Your signal lights aren't really 'blue' then. Generally, when we talk about lamp colour it is while illuminated.

I callz em like I seez em

Shadowfax, can you combine all your topics into one from now on instead of posting multiple topics within a day or two in the same section?

The headlights you posted a pic of are projectors. Yours are reflectors. Absolute opposite in how they cast the light to the road.

That'* what I was thinking as well. Our headlights already have the black plastic insert in them that creates a little of the effect you are looking for.

If you're going to paint your headlights black like I have, you NEED projectors...thats the ABSOLUTELY ONLY WAY that will work

Kind of a bad pic but you can see its painted black




With the Projector in action (((( OLD SET UP ))))