1965 C10 Turquoise Interior
 

Working on a '65 that originally was turquoise but someone long ago in a far away galaxy painted it maroon. The truck has the custom tag and paint code 540. I found a site that shows the interior of the truck should have been turquoise. I thought they were all fawn with a few exceptions, anyone know if this is true? Can't seem to find any pics of mid 60's but found several '67 and later. There is a PDF file attached that shows the the color combinations too

Re: 1965 C10 Turquoise Interior
 

If your truck is Chevrolet C10, it was fawn on the inside. That chart pertains to Corvair trucks. For C-10's and C20's at least, fawn was it. Only possible difference was a red trimmed seat if the outside of the truck was red , white, or gray. Examples of those are very hard to find these days.
GMC is different. Those trucks had a few options, with turquoise being one of them. Not sure on the what our why for GMC seat and dash colors, but they did vary a little.
Bottom line for your 510 turquoise C10 is that it was fawn with a black floor mat.