I picked up these TB-13 tabs recently. I recall seeing a set of tabs in blue, and with the 1969 Catalog featuring the blue color theme, I thought that may have been an original color for them. These TB-13 turned out to have been originally silver in color.
These still have the BIS for Bethlehem Steel on the bolts! I think it is kinda neat they have hung around together all these years. FYI, the TB-13 are for 1968 GTO.
Here they are next to some TB-9 tabs for 67/68 Camaro. I think the silver color on these is original.
Interesting the rounded tab is so much smaller between the two.
So these TB-13 tabs were originally silver. They were painted blue with overspray and such on the bolts. Though there seems to have been a few colors NMW painted their tabs, I stand by my opinion that there is no wrong color for them. Many of the end user's painted them to suite the theme of their car.
To be honest, there is a part of me that likes the tabs and bar to match in color. If you have a bar that is nice enough "as is" I might just try and match that. Otherwise paint them all to match. You can't go wrong with anything you do to them.