Question:

How can I find a good color palette for my plot?

Example: 

Custom color palettes for ocean-temperature, values centered around zero, gray-scale, and customized for topography/bathymetry.

The above illustrates several palettes used to plot SST and topography. Here is the Ferret script:

! Plot sst
 USE coads_climatology
 SET REGION/L=1

! The ocean-temp palette
 SET VIEW ul
 FILL/NOLABELS/PALETTE=ocean_temp sst; GO land

! plot temperature minus mean with a centered palette
 SET VIEW UR
 FILL/NOLABELS/PALETTE=white_centered sst - sst[x=@ave,y=@ave]; GO fland

! use a greyscale paletete
 SET VIEW LL
 FILL/NOLABELS/PALETTE=greyscale sst; GO land

! plot a relief map using the land_sea palette
 USE etopo120
 SET VIEW lr 
 FILL/NOLABELS/PALETTE=land_sea rose

Explanation:

A number of palette files are available with Ferret. They are designed to highlight different kinds of data fields and to allow sets of plots to have a standard appearance. Some trial and error may be necessary to choose the palette that looks best on a given printer or other output device. A variety of palette files are illustrated below.

See the Ferret Users Guide, the Section on the PALETTE command, and in the section about customizing plots and palette creation, for more on specifying a palette with the plot commands, and about the different kinds of palettes. There is also a palette_demo.jnl script about the different kinds of palettes.
 

In the scientific graphics community, there is much discussion of best practices with color palettes. Here are some references which discuss the shortcomings of rainbow palettes, and good alternatives. Some of these alternatives are included in the Ferret distribution and are discussed in the FAQ's listed below
http://www.climate-lab-book.ac.uk/2014/end-of-the-rainbow/
A Better Default Colormap for Matplotlib, https://youtu.be/xAoljeRJ3lU

Also see these related FAQ's,

• Howcan I produce a plot with both colors and patterns? for an example using the pattern fill and shade keys,
• Gotany good ideas for black & white graphics? for a discussion of filled plotting using black and white palettes and patterns.
• Which of Ferret's color palettes best convey information to color-impaired viewers?
• What palettes will show up well if I photocopy the output, or display it using LCD projectors, Laptop and CRT screens, and color printers?
• How can I create a palette to show out-of-bounds data?

Here is a table showing a range of available palettes with examples. For the Percent palettes, a range of colors is shown.The Levels and Values palettes are shown with examples from datasets to point out their advantages.

Palette name	Description	Type of Palette	Example Plot
default	The default palette; The viridis palette	percent
rainbow	The rainbow palette	percent
ocean_temp	Shows range of ocean temperature by value, so plots with different ranges of values will have the same colors for given temperatures. These two plots are the same except for the region. The same color represents the same temperature in both.	value
dark_land_sea	For topography/ bathymetry plots. Brown and green on land, blue for sea	percent
land_sea	A lighter palette for topography/ bathymetry plots	percent	l
ocean_blue	A range of blues for bathymetry plots	percent
dark_terrestrial	A range of green and brown for topography plots	percent
terrestrial	A lighter palette for topography plots.	percent
modulo	A palette whose colors on either end match	percent
inferno	inferno palette, based on matpltlib and R palettes	percent
magma	magma palette, based on matpltlib and R palettes	percent
cmocean_algae	algae from cmocean perceptually-uniform colormaps	percent
cmocean_amp	amp from cmocean perceptually-uniform colormaps	percent
cmocean_balance	balance from cmocean perceptually-uniform colormaps	percent
cmocean_curl	curl from cmocean perceptually-uniform colormaps	percent
cmocean_deep	deep from cmocean perceptually-uniform colormaps	percent
cmocean_delta	delta from cmocean perceptually-uniform colormaps	percent
cmocean_dense	dense from cmocean perceptually-uniform colormaps	percent
cmocean_gray	gray from cmocean perceptually-uniform colormaps	percent
cmocean_haline	haline from cmocean perceptually-uniform colormaps	percent
cmocean_ice	ice from cmocean perceptually-uniform colormaps	percent
cmocean_matter	matter from cmocean perceptually-uniform colormaps	percent
cmocean_oxy	oxy from cmocean perceptually-uniform colormaps	percent
cmocean_phase	phase from cmocean perceptually-uniform colormaps	percent
cmocean_solar	solar from cmocean perceptually-uniform colormaps	percent
cmocean_speed	speed from cmocean perceptually-uniform colormaps	percent
cmocean_tempo	tempo from cmocean perceptually-uniform colormaps	percent
cmocean_thermal	thermal from cmocean perceptually-uniform colormaps	percent
cmocean_turbid	turbid from cmocean perceptually-uniform colormaps	percent
rainbow_by_levels	A variety of colors assigned by level: each level gets one color. The LEVELS qualifier is used to specify six levels for the first plot and eighteen for the second.	level
rnb2	Another rainbow of colors with fewer greens	percent
saz2	Yet another rainbow of colors	percent
light_rainbow	Similar to rainbow, but with washed-out lighter colors	percent
broad	Designed to distinguish levels over a broad range	percent
no_blue	Palette with no blue tones	percent
no_green	Palette with no green tones	percent
no_red	Palette with no red tones	percent
low_blue	Palette with low amount of blue	percent
low_green	Palette with low amount of green	percent
low_red	Palette with low amount of red	percent
centered	Distinguishes values above and below the middle level; warm colors above and cool colors below.	percent
centered diff	Distinguishes values above and below the middle level; bright colors with warm colors above and cool colors below.	percent
white_centered	Another centered palette with white as the central color. A variation on this is to make a copy of the palette file and create a similar one where white is replaced by very light gray, to distinguish it from the white of missing-data.	percent
grayscale (also greyscale)	Series of grays	percent
inverse_grayscale (and inverse greyscale)	With high and low reversed	percent
bluescale	Series of blues.  See also redscale, greenscale,reverse_bluescale, and so forth, which are the same palettes with high and low reversed.	percent
Single colors black blue blue_light blue_dark brown brown_light brown_dark cyan cyan_light cyan_dark gray gray_light gray_dark grey grey_light grey_dark green green_light green_dark magenta magenta_light magenta_dark orange orange_light orange_dark pink pink_light pink_dark purple purple_light purple_dark red red_light red_dark tan tan_light tan_dark violet violet_light violet_dark white yellow yellow_light yellow_dark	One color in the palette. These are useful for colorbars, filling between curves, making backgrounds, and filling polygons to make different colored dots on a plot, as in marking station locations. For examples see the FAQ: Howcan I fill between two curves? and the Ferret v5.6 release notes		for instance, violet   or to color symbols on a map: go polymark poly/over/line/pal=pink xpts,ypts,,square go polymark poly/over/line/pal=orange_dark xp,yp,,circle