I do not stock cushions because I fear if I do pick a few cherries that my staff will ask me for a specific size and col / clarity.
Then we face loss of face by supplying lessor cut quality or loss of business and lower morale when i say "sorry, all the stones I can find are dross"
The problem is that there is no one well cut cushion as cushions come in several types and facet patterns.
Each can have a different IS/ASET appearance when well cut.
In the IS I would look for min. white and a pleasing mix of black and red.
The aset is a little more complicated but In general I would look for a lot of red, little white/black(depending on aset type) with some blue and green thrown in for contrast.