Hi Barb – I personally think that the seller should disclose ALL information about the solid before you buy. That's what would happen in a store – you wouldn't buy something without looking at it and buy it if it had a 'fault' – or if there were another that didn't have 'discolouration', you would buy that one.
Although other members do not think that it (discolouration) affects the value of the solid, I think they'd agree that it's far more pleasant to have one without discolouration that one with.
And if that's so, why would the seller take $20.00 off??
In my experience, I have obtained solids with discolouration much cheaper than those without, just because the seller wanted to get 'rid of it'.
I would also be upset if the seller didn't tell me the actual condition before buying.