Check the white (monitor adjustment) sheet stapled to the inside of the back door. Does the upper right hand say "TKG-UP" or does it say DJR1-UP"? If DJR1-UP, Are there staple holes from a previous sheet being put there?
The tags were often switched out for field conversions, so you might see a VS tag in place of a DK tag but that doesn't mean the game was never a DK. It was less common for operators to switch out the monitor adjustment sheet on the inside of the back door.
It's entirely possible that some blue DK Jrs were out there, the Japanese flyer even shows DK Jr. in a blue cab. However, I'm not sure we've ever had good "proof" of a blue DK Jr.
In most cases the original poster never follows up or posts pictures or replies with a vague answer of some sort.