Not sure if this has been suggested in the past, but it would really help if we could filter by color identity. Creating commander decks would be much easier if we could filter out cards that have additional color identities compared to their actual color. Cards like Morophon not being in every colorless filter would make things a lot cleaner.
Its not clean, but if you do "rules text:" select either include or exclude, and then the color coes you want/don't want to see in rules text, it'll filter as such.
For example, once I've narrowed a list to just commander/brawl/singleton legal within the colors i want, then I go and (ina second tab) copy that search. In second tab, add the "rules text" to filter cards that include colors I don't want to see (there will be a few false positives, but not many). From this, adding the following filter to first tab "name - does not contain:" and listing the ones I cannot add (again, if you've narrowed tab 2 proparly, it should not be a long list), then apply filters. Finally I save the search (just in case I need to return to it) and begin the hunt.
Is it elegant, no, but it does work.