is it illegal for me to ship a magpul d60 to colorado? or is it just illegal to own them there? I have a guy wanting to buy one.....

On the books there is a law prohibiting residents from acquiring mags with a capacity larger than 15rds. With that said you have zero chance of being prosecuted for shipping a mag into the state. Nearly every gun store has 20, 30, 60  etc. round magazines new in wrapper on the shelf and in 55 gal drums for sale. They are in plain view of all LE and government officials that enter the store and nobody has been arrested/charged/cited for it since the implementation in summer 2013.

More succinctly, it is technically illegal for the CO resident to possess it, but not for you to sell it or ship it to them, since you are not a resident of Colorado, nor is the sale taking place inside the borders of the state.

Also shops are selling broken down 30, 40 rd mags as kits (body,springs,follower all in one bag)

And I bought an AK a while back and was given 2x 30rd magpul mags with it

Local shop down the street has approx 20 of the d60's sitting on there shelf with just about any thing else you want.

With all the magazines available there why would anyone go to all the trouble of wanting one shipped in? Smells fishy to me.

Price, as with most stores around the country they're asking too much.