[MR] varnish question

[Jennifer Dobyns]

Greetings,

To those artists on the list, I pose a question:

Is there such a thing as varnish which does not "yellow" over time?  I 
just found out one of my projects has changed hands and the new owner 
described colors which I did not remember using.  It was a painted 
canvas floor cloth that was varnished with a commercial polyurethane 
which has apparently yellowed over time to make antique white and blue 
turn into creamy yellow and green!  I would like to find something that 
doesn't do that if possible.  Interestingly enough, it apparently didn't 
change the red that much.

And for the really curious, the polyurethane I used was probably made by 
Minwax.

A somewhat perplexed,

Jen Dobyns