Some countries got the 69 model in white if that makes any difference.

I know RS sell a paint. It's water based and hard work to get the finish right. I have used it a few times. It's also not very good around ethanol fuel. Guess how I know that. You can put as much spray max 2 k lacquer on as you like but it gets at it and bubbles it up.

You know what Mark, I don't even know if the DT1 came to the UK in it's original form. I know it got to France and sold ---- 21 
it has to have the tank done no matter what. It looks like the po painted over corrosion and it looks bloody awful despite the good job and quality of the paint.

I don't know either... my point was "white" could be considered an original 69 color if you decided you liked it better. I think Australia/New Zealand got the pearl white in 69? At least I vaguely remember reading that here and maybe seeing a brochure? If what you have is confirmed to be a USA market model and you want to make it original, then don't go with white.

Isn't the paint designation carried in the chassis number?

Paint is not "coded in" to the chassis number if that's what you mean?  

In later years other countries seemed to get different prefixes but in the early years I'm not sure what Yamaha did, if anything, to the VIN number to distinguish a model sold outside the US?  It seems models in other countries sometimes had numbers outside the range of the US models but that doesn't seem to always be the case...  again especially in the earlier years.

One clue is that a non-US model probably would have come with the longer seat that had the grab strap for the passenger.