IDL colourtables

IDL has a selection of about 40 built-in colour schemes. You can load the fifth one of these, for example, by doing:

IDL> loadct,5

(as we did for colour table 39 above). To return to the default grey scale, do:

IDL> loadct,0 ; greyscale

Or a simple rainbow

IDL> loadct,39 ;rainbow 0=black, 255=white, 220ish=red, 50ish=blue

Most of these built-in schemes have colour 0 as black and colour !D.Table_size as white. It does matter which colour table you use when plotting data. Many (eg 39 above) doesn't give good contrast in all areas (e.g. around the greens). This leads your eye and brain to see the red/orange/yellow data as different and the green data as all the same - misleading! I personally like one I picked up from someone in Edinburgh (which he stole from somewhere else). See

~lecjm/IDL/Procedures/Display/load_sst_ct.pro

if you would like to use it (see ``Colour images'' for an example).