Path: utzoo!dciem!mmt
From: mmt@dciem.dciem.dnd.ca (Martin Taylor)
Newsgroups: comp.cog-eng
Subject: Re: The use of Red and Green
Message-ID: <2958@dciem.dciem.dnd.ca>
Date: 1 Mar 90 23:31:38 GMT
References: <44532@lanl.gov> <5468@bgsuvax.UUCP> <3037@draken.nada.kth.se> <1017@m1.cs.man.ac.uk>
Reply-To: mmt@dretor.dciem.dnd.ca (Martin Taylor)
Organization: D.C.I.E.M., Toronto, Canada
Lines: 30


Peter Crowther mildly flames the idea that there might be a problem in
allowing per-user user-controlled default colours for signifying correct
and wrong answers.  The original poster had noted that the conventional
red and green were confusable by colour-blind people.

It is NOT a good idea to let users choose their own colour codes.  They
almost always do it wrong (and there is no value judgment in that word).
Even paid consultants often do it wrong.  So when colour coding is to
be used, the colours should be chosen with some insight into the capabilities
of the visual system, and of conventional coding patterns.  In respect of
the colour-blind failure to discriminate red and green, there are two
main types of red-green blindness, distinguished by having different lines
of colour confusion in the CIE diagram.  Look them up in a handbook, and
choose colours that lie athwart both sets of confusion lines (from distant
memory, I think a yellowish green and a mauvish red should be OK, and
should be distinguishable also by the rarer blue-yellow blind people).

I once visited an Admiralty research laboratory, and was shown a fairly
complex display.  I asked why they had used certain colours, and suggested
some changes, which were made on the spot.  A few months later, I got a
message saying that my half-hour visit had done them more good than the
substantial contract that had led to their original colour codings.  To
code colours, I emphasize, you have to know what you are doing.  Don't
let the users select whatever pretty set they want, because as like as
not, they won't be able to do the work they are supposed to do.
-- 
Martin Taylor (mmt@zorac.dciem.dnd.ca ...!uunet!dciem!mmt) (416) 635-2048
"Viola, the man in the room
doesn't UNDERSTAND Chinese. Q.E.D."  (R. Kohout)