The fact is, that the colors of the Z1's screen are not dull, they are realistic and true.
I had an S2 myself and it shows completly wrong, unnatural and oversaturated colors. When you've used an S2 for a long time, you'll get the impression that normal colors are dull, when in fact they are not and the S2 colors are wrong.
That's the problem.
Sony Xperia Z1 white (root, .534 firmware)
Ericsson T65 ('01-'04) - NEC e616 ('04-'05) - Sony Ericsson K750i ('05-'06) - Samsung D830 ('06-'07) - Sony Ericsson K850i ('07-'10) - Nokia E51 ('10 - 2months) - Sony Ericsson Vivaz ('10-'11) - Sony Ericsson Xperia Arc ('11-'12) - Samsung Galaxy S2 ('12-'13) - Sony Xperia Z ('13) - Sony Xperia Z1 ('13-?)