Hi Nile,

I've followed this ng for some years and yours was first post I've read to
give informed comment on the issue of colour blindness. Apart of course from
Jim's addin. Whether 3% are affected or nearer 10% (the average of various
articles I've read) is immaterial. Even 1% of Excel users represents a very
large number.

I'm surprised this issue as relates to Excel has not been discussed more, eg
traffic light red & green are frequently used and liable to confuse. But
others are affected by different combinations.

It seems to me there are two solutions:
- Ensure all spreadsheets use colours that can never be confused, I think
unrealistic.
- Affected user adjust colours to suit. In Excel it's is very easy to
customise the palette and in turn update colours in use in the workbook.
Except it isn't as Excel provides a minimal and laborious interface to do
that, nor an indication of used colours other than in the selection.

Whilst I'd never advocate over use of colour in a spreadsheet, Excel has
fantastic and un-exploited possibilities for doing things with colour. For
certain purposes more useful even than other applications designed
specifically for colour processing.

I have also written to you off-line.

Regards,
Peter T


"Nile_Hef" wrote in message
...
An interesting post, my understanding is considerably more than 3% are
affected to some degree.

The 3% figure holds good for the adult male population of the United
Kingdom
and the continental USA, and it is the number quoted by Ben Shneiderman in
'Designing the User Interface'. Some places have higher incidences of
dichromat colour-blindness: Wikipedia quotes an 8% figure for Australia!

I've only ever written a spectrum-shifter as bespoke code for Excel users
on
a 'by request' basis and I had to work it all out from scratch - the worst
part being the need for a hand-rolled 'effective wavelength' metric for
RBG
codes as perceived by healthy trichromat humans. Those neat triple
bell-curves of frequency versus sensitivity for the human retina are the
start of a very, very messy calculation.

The code is owned by a former employer of mine and will never see the
light
of day again. I've asked if I can put it in the public domain and all I
ever
got was boilerplate pro-forma statements about banking confidentiality and
the threat of legal action.

Anyway, your idea of a user-configurable frequency shift is an interesting
approach, and a surprisingly difficult user interface design problem: none
of
the popular graphics packages (Paintshop Pro, Adobe, CorelDraw) has a
colour
manipulation dialogue that does exactly what you want with images, and
GIMP
has a particularly loathsome 'curves' screen under the colour tools menu.

I am not the most systematic and disciplined of beta-testers but I'd enjoy
seeing your application. I can't get at my personal mail accounts from the
trading floor, but feel free to mail me as Heffernann yah oo dot com


Regards -

Nile