[B]Legal or not Legal[/B]
 

Yes, illegal
I assume you mean black opaque ?
DOT requires working turn signals and side markers

You mean tint them so they still work normally but look black or close to it when the light is off? I'm guessing it differs state to state whether or not it's technically illegal. I'd suggest going with a smoked film instead of spray on stuff so you can easily remove it if you get pulled over. I THINK they have to reflect light as well as letting light show through, and I'd also assume they have to let a certain amount of light through.

Just remember, the side markers are there so people can see you and know where you are turning.