Gee! Thank you all for the unexpectedly impressive response. Particular thanks to tsuwm, the link was very clear in enlarging on maverick's reply.

Thank you AnnaS for prodding so well on the colour issue. Not sure we've bottomed that out yet. Jazzoctopus' statement that green is the colour most distinct from red intrigues me as I am red/green colour blind which would have led me into the natural mistake of thinking that the wavelengths of these two colours must be close. Still its many years since I studied physics so perhaps I can be forgiven. But I'm still puzzled and will pursue further.

BTW, "out of pocket" in the sense of out of touch is used in the UK, in my experience, by those who aspire to be taken for City whizz-kids. Apologies to any Brit AWADers who may be fond of using it - I'm sure you really are City whizz-kids!.