Streamline coaches with black or grey roof?

Some pictures I've seen seem to show some of the NYC's corrugated-side cars with either black or dark grey roofs. Were they painted this way or is it just weathering or possibly lighting? I seem to remember seeing some models of those cars with black roofs also. What is the correct scheme(s- I'm sure there were probably more than one) for these cars?

Here is a similar question & response that was posted 4 years ago:

Posted by ron morse on Sun, Sep 10, 00

I have seen several references made to the color of streamline passenger car roofs(fluted side-fluted roof and smooth roof).Some sources say they were painted black,others say they were just dirty from the coal smoke! Has anyone seen official paint diagrams showing correct color in the late 1940 to early 1950's period? ...

Posted by JT Roberts on Tue, Sep 19, 00

The "goop" was a material refered to as F-6 Car Cement. This is the same material that was used on caboose roofs and on passenger underbodies. (passenger CAR underbodies, before anybody asks how they got passengers to hold still for an application.) The Budd roof seams opened up over time and they leaked.

The problem never truly went away, but by the 1970's a colorless roof sealer was used. It may have been some sort of polyurethane. It could be applied with a mop and after it dried it remained flexible.