The Iris Database handles color a couple of different ways.
The "Bloom Color Description" field is basically a copy of the hybridizer's description of an iris when it was registered with the American Iris Society. I believe AIS encourages hybridizers to use the RHS color charts when describing an iris flower, but most do not. Altogether, I've seen at least a dozen different color classification systems used by various hybridizers and many, including a number of famous hybridizers, don't use any classification system at all.
We also have a "Bloom Color Classification" field in the database, which is essentially a simplified color chart included as a search aid. For, example, if you searched the "Bloom Color Description" field for for yellow irises, you wouldn't find those irises described by hybridizers as "lemon", "mustard", or any of the other synonyms for "yellow". But, all of those lemon, mustard, etc. irises could found by searching for Yellow in the "Bloom Color Classification" field (or, more accurately, will be once the Iris Database is fully updated).