[gradsusr] transparent colours

[Becker, Bernd]

Hello!

How can I define transparent colours, 
that produce visualy distinguishable hues when overlapped?

I would like to define areas on shaded plot that are,
say, windy and warm, and where these areas overlap
I would like to visualize that the ovelap area is windy and warm,
without
having to define another colour for that specific region. 

Rather than defined colors by RGB, I guess, I am asking if it is
possible to 
define colours in grads using the HSLA colour model.

best regards,
Bernd.


--
Bernd Becker   Climate Impacts Product Development
Met Office Hadley Centre    FitzRoy Road  Exeter   Devon EX1 3PB  United
Kingdom
Tel.: +44 (0) 1392 884511 Fax: +44 (0)870 900 5050
E-mail:bernd.becker at metoffice.gov.uk -
http://www.metoffice.gov.uk/research/our-scientists/seasonal-to-decadal/
bernd-becker