Hi Charlene
All of the Primary and Secondary colors are in DMC's lineup!
But when I read your question, I had a different thought in mind as to what you were asking.
I was thinking more along the lines of DMC mainline colors vs their hard to find colors, and why so many kit projects use the same color groupings.
Another question could be, how do stores that do not stock the full line of DMC colors determine which colors they will stock. Some stores like WalMart for example, sell kits that contain colors WalMart has never carried and never will.
Not available to the general public are popularity lists of floss colors, based on the sale of those colors. If you were opening a store and opting to carry DMC floss in that store, you would get such a listing for inventory control.
When my aunt opened a small five and dime, she planned on carrying a standard line of sewing threads. Coats and Clark provided her with a listing of display units of various sizes that held pre-determined color groupings. The smaller units only carried their prime movers, while the larger units were based on the percentage of sales of certain colors to determine which colors were determined for that display unit. The distributor for Coats and Clark strongly suggested against carrying the full line due to the value of floor space weighed against colors that did not sell well.
But by another viewpoint, if I plan on frequenting a LNS and supporting their business, I expect them to carry the FULL DMC line and most LNS try to. But DMC (or their distributors) are very lax in maintaining inventory to keep the LNS's supplied. One local LNS showed me her order list vs what was sent by the supplier to her. More than 1/3 of the DMC colors she ordered were scratched off her order as being currently unavailable. So it's not always the LNS's fault they are short on color selection.
TTUL Gary