In order to use a palette load it at the beginning of your gnuplot file via
load 'palette.pal'
Replace palette
by the name of your desired palette, which are listed below.
Note, that this will not only define a palette, but also overwrite the first
eight line styles. If you want to use your own line styles, you have to define
them after the above command.
If you need more help, have a look at this example.
Most of the palettes are from ColorBrewer and were first ported to gnuplot by Anna Schneider.
If you look for a good standard palette try moreland.pal
, which comes from
Kenneth Moreland.