Colour Attributes

The Colour attribute can be used to specify the colours of various components of a plot. The value assigned to the attribute can be:

• An integer colour index. Colour indices can be thought of as `pen numbers'. For instance, the string "Colour(border)=3" says ``Draw the border using pen number 3''. The resulting colour depends on the colour of pen 3, which can be set using PALENTRY.

• A standard X colour name, e.g. "Colour(border)=red".

• A triple of floating point red, green and blue intensity values in the range zero to one, separated by spaces, e.g. Colour(border)=1.0 0.0 0.0.

• An HTML colour code. This is a hash followed by 3 pairs of hexadecimal digits giving red, green and blue intensity in the range 0 to 255, e.g. "Colour(border)=#ffa700". Within style files, the "#" character is used to introduce a comment, and so the colour code would be ignored. To avoid this, the "@" character can be used in place of "#".

If no pen is currently available in the palette with the requested colour, then the `nearest' colour will be used instead--sometimes this may not be very near at all! If you specifically want the requested colour, then you should use PALENTRY first to set one of the available pens to the required colour.

Note, if you produce a plot on an X-window and then change the representation of pens using PALENTRY, then any components of the existing plot which were drawn with the modified pens will change colour immediately if an only if your X window is set to 256 colours (i.e. if you have an 8 bit pseudo-colour visual). If you have a 16- or 24-bit display, then changes to pen colours will only affect subsequently drawn graphics.