Why have colored disks?! You do know that won't be able to see them inside the metal, hermetically sealed covers!
OTOH, it might be fun to watch the arm mechanism moving to each track. Perhaps the edge of the disk has contrasting color bands and a strobe light inside that would tell you if it was spinning at the correct speed like those fancy turntables!
Just make sure the pre-asymboled units state the brand of drive and, more importantly the model. Simply saying "Seagate" or "Toshiba" is not enough. That's why the warranty length will help.
Also consider the connection method. If you have USB 3 on your Mac, don't be tricked into buying a USB 2 only drive unless you can live with a very slow speed. Slow speed may be OK if the drive only creates small backups while you do other things, but frequent access (reads/writes) while working with graphics may not be much fun!
Lastly, if you can afford
two drives, get
one for TM and
one for a cloning (bootable) backup. 2TB minimum, 7200rpm, 3-5 yr warranty, largest cache you can get, USB3 at least (it will work on your Mac, even if it has USB2).
Enclosures seem to have increased in price. OTOH, there are now dual, drop-in "enclosures" for <$32. Those drop-in boxes make rotating backups extremely easy, but I fear the cheap ones are Asian knock-offs. Buyers beware.
Does anyone have warranty info on the Seagate portable drives mentioned further up this thread? Only info I could find with a minimal search was for bare drives.