Spirit changed the livery to coincide with their new marketing effort as an "Ultra Low-Cost Carrier" (or ULCC) ... the pixel livery appears to "classy" for a ULCC, hence the new colorful design (which I'm not exactly a fan of, either).
For pictures, check out the main thread on Civ Av. Search for Spirit. (I'm too lazy to link anything right now.
I'd take the awe of understanding over the awe of ignorance any day.