Actually, the two outfits are, in fact, not the same. They're both green and gold, but the similarities end there.


As you can see, his outfit in KQVI has somewhat puffed-out sleeves with cloth of gold in stripes down them, while his outfit in TSL presents rather different sleeves. Also worth noting is that the front of Alexander's tunic is decorated in TSL, but plain in KQVI. All that this thread has really proven is that he has a penchant for green and gold (which isn't unreasonable; I like them too).
Now, this is an adventure game. Let's remind ourselves that Graham has endless pockets; if we're going to complain about the lack of realism, let's start there.