yeh my phone is exact same..

i first noticed it when i was in my room at night, all lights were off.. and i was restarting the phone.. and noticed that the 'black' background had random black dots everywhere (so clearly the black background is slightly lighter)
and then even when turning the device back on and you have the nokia thing with ripples, you could clearly see that there were colour issues, heaps of random black dots everywhere...
and if you carefully look and take notice, even during the day you can see the not fully blended colours in this start up screen


ALSO! yes, i have those purple lines as well...

iv never thought about taking it in for a replacement though... maybe i should..
but iv done my music, contacts, calender and everything already.. i really cant be bothered doing it again on a new device (which might still have the same problem....)

but if this REALLY isnt meant to be like that.. then.. i guess its good to take in
i checked with my friend who works for a phone carrier... and she said wait a few months, its still under warranty and get replacement, that way there is most likely a slightly updated device that will have a few other bug fixes