oh dear, I am just now seeing this thread.
I really do like the concept of a color challenge! (great idea, Laramie) I have hosted a few color challenges in years past, though more so to get people to improve their skills by trying to pick colors in relationship to other colors on the color wheel (complimentary, tri-ad, etc). I do, however, know that it is hard to match colors exactly... and I have learned a few things over the years. While there are tools that will allow you to get the exact color of a swatch online (e.g. the color picker on PSE), and some people who are skilled at altering elements might be able to match said colors (I am not one of them... I have a hard time adjusting colors!), I've also learned that it's not always wise to do so for printing reasons. What looks nice on a computer screen doesn't always print the same color (out of gamut). So many times it may be a good idea to use the products you have purchased from a designer (and hope they have tested for gamut). That said, some people may not have the exact shade in the swatch, and I'd hate for them to spend money on additional products to get a shade closer when they might already have a set of products they trust. Now I like to leave it up to hosts/those who donate products to have the final say on what is acceptable in a challenge, but I just wanted to say I'm personally okay with colors not being exact... if they have made an honest effort to try to be close.
Laramie - thanks again for hosting... I really appreciate it!