Ahh yes the car crash that is WD's naming convention - if memory serves me well it goes something like this:
Blue is your bog standard consumer grade drive - the old 1TB 7200rpm blue were very good drives for what they were - IIRC anything larger is just a rebadged 5400rpm green and therefore pretty knack.
Green are now blue and were the eco drives - best avoided.
Red is a NAS optimised drive, better durability BUT there are two versions the pro which is the best and the standard red which has the unfortunate power saving mode. The Pro is generally considered more reliable the standard reds are a mixed bag.
Black was the super fast performance gaming drives - however in some cases the 1tb blue out performed them because of the single platter. Generally i believe they have better endurance and come with a longer warranty.
Purple is optimised for CCTV, they are slower drives designed for 24x7 writing and do the job well but you wouldn't want use them for anything else.
Gold are the Datacenter line and basically WD branded Hitachi Ultrastar - excellent drives but pricey and I'm not sure if WD are even still making them.
Then you have the white label shucked ones which can be anything but most probably red or green.
TL;DR
Get the blue 1Tb if you just need a basic drive, otherwise get the Red pro if you are feeling flush and want reliability, or the standard Red if you just want cheap storage, but make sure you have a good backup if you do.
If you can get gold at a good price, go for them instead.
I have a Red for general storage which backs up to a Gold for archive purposes.
Please note WD like to change everything without telling anybody but keeping the same names, so research the actual model you are looking at as it may be a different story for that particular drive.