That looks like a purple tinge to me mate! Anything other than the top colour is very bad.
I take it you're fishless cycling? If so, I'd say your nitrate reading is just as important right now as it shows the ammonia and nitrite are being broken down successfully with a steady increase.
To be on the safe side for when you do add fish (I really do hope there isn't any in the tank right now!) I'd invest in some Seachem Prime. It's a water dechlorinator but also makes ammonia, nitrite and nitrate non-toxic to fish should any ever appear. They will however still show up on test kits to help you solve the problem. I can't recommend it enough, definitely saves lives!