Opinions - Crystalline methamphetamine with a twinge of brown

[Dexyfiend]

SWIM's friend just bought a fair whack of meth and told SWIM that it has a slight brown colour to it instead of being clear (or at least white).
Whats the deal with this???
Yes, SWIM knows whatever is said will be purely speculation but is asking if anyone else has either:
a) Come across something similar themselves
b) Synthed meth in a dream and came up with slightly brown dope
c) had any problems(adverse effects) from such product.

OR if anyone knows for a fact which cut/impurity is synonymus with the colour brown (probably lots)

Now SWIM has whacked coloured amphet sulphate and freebase on many occasions (swim is an idiot speed freak) with no ill effects so is not worried hugely he's just curious. He realizes he could do an acetone wash but a) dosent have any b) is planning to aquire such a small amount; less than .2 grams, for it to be futile.

Any opinions would be greatly appreciated