oops missed one on my colour quiz list!

[snoopyfan]

Used regularly by Poirot
( I did wonder if it could be "Red herring" but have this as answer to "An irrelevant distraction")so that may be wrong!!

[smouse]

little grey cells

[snoopyfan]

thank you, I work in a library but don' read thrillers!

[swannbaker]

Miss Lemon .

[snoopyfan]

seem to be two good answers for this one!!!

[kettledrum]

I don't think he 'used' Miss Lemon, but he definitely spoke about using little grey cells !

[snoopyfan]

good point!!!

[swannbaker]

What's a woman for if not to be "used" ?
Definition : Use = Employ .

[kettledrum]

Swannbaker - Yours, of course, is the witty answer, but I think 'used regularly' tips the balance towards 'grey cells'.

Now ... if the question had been 'employed by Poirot' !!