Cubehelix

The "cubehelix" option defines a family of palettes in which color (hue) varies along the standard color wheel while at the same time the net intensity increases monotonically as the gray value goes from 0 to 1.

     D A Green (2011) http://arxiv.org/abs/1108.5083

start defines the starting point along the color wheel in radians. cycles defines how many color wheel cycles span the palette range. Larger values of saturation produce more saturated color; saturation $>$ 1 may lead to clipping of the individual RGB components and to intensity becoming non-monotonic. The palette is also affected by set palette gamma. The default values are

     set palette cubehelix start 0.5 cycles -1.5 saturation 1
     set palette gamma 1.5