Well, my situation finished up on a positive note. After a short time on the phone with someone at AT&T, we discovered that the retail manager canceled my contract renewal, but not the hardware order. (Although since the phone went out already, I doubt he could have canceled it, but anyways...) After some discussion, we decided my best course of action was to return the phone bought at the Microsoft store and keep the phone that AT&T shipped to me. This will allow me to still receive the wireless charging pad and expedite getting my money back for paying for two phones. She also credited my account for the not-so-overnight shipping I paid for, as well as funds to account for a restocking fee in case the Microsoft store dinged me for it (which they did not...yay!). So in the end, I have roughly $60 in account credit, a spare LTE SIM card, a charging plate coming my way...and my yellow Lumia! Yay!
Now to figure out how to use this thing...this is SO not an iPhone.
And for those still curious about the color, here's my print shop training coming through: I'd compare the color of the yellow Lumia to an Astrobrights Lift Off Lemon, and the yellow theme in WP8 akin to a Solar Yellow shade. Beautiful individually, but not so great together. I've actually ended up using the lime theme in WP8. It's no lemon, but at least they're the same neon-like intensity.