Full Idea
We are aware of the universal 'yellow'; this universal is the subject in such judgements as 'yellow differs from blue' or 'yellow resembles blue less than green does'.
Gist of Idea
We know a universal in 'yellow differs from blue' or 'yellow resembles blue less than green does'
Source
Bertrand Russell (Knowledge by Acquaintance and Description-1 [1911], 154), quoted by Bernard Linsky - Russell's Metaphysical Logic 2.3
Book Reference
Linsky,Bernard: 'Russell's Metaphysical Logic' [CSLI 1999], p.34
A Reaction
This still seems one of the strongest examples in support of universals. You could hardly be talking about yellow tropes in such instances (even if the world does contain yellow tropes).