The best place to look for information about Glock label colors is Glock's Minimum Advertised Price (MAP) list, FRM-26-38. There's one that is a year old available for download here:
http://www11.davidsonsinc.com/ManufMaps/Glock-MAP-Pricelist.pdf
From that it can be seen:
RED - High-capacity magazines. Advertised sales price is governed by Glock's MAP.
WHITE - Ten round magazines. Advertised sales price is governed by Glock's MAP.
PURPLE - Specific pistols designated by Glock. Advertised sales price is NOT governed by Glock's MAP. (This can be any pistol that Glock wishes to move quickly (like production overruns) without compelling dealer use of MAP in his advertising.)
ORANGE - Factory rebuilds and refurbishments. Advertised sales price is NOT governed by Glock's MAP.
Not on the MAP list is:
BLUE - Discounted and often specially-configured pistols for sales to a broad spectrum of public safety personnel. Pistols normally supplied with MINUS connector and adjustable rear sight will usually have the UNMARKED or DOT connector instead, and a fixed rear sight. See:
https://us.glock.com/buy/blue-label-program
There are NO special label colors for USA-manufactured Glock pistols.
NB: Glock can place NO limit on what price a dealer sells a new pistol. A new G40 can be sold for $5. But the dealer may not advertise the G40 for that price. When a dealer wishes to advertise pistols governed by the company's MAP list for a lower price than the MAP list allows, there will be a "Call for price" notation in the advertisement.