Watercolor is the perfect medium for experimenting with color palettes.
I use a juicy brush with plenty of pigment and water and stroke it on to a piece of Arches 140# cold press paper. Next to it, I stroke a second color, then a third. Finally, I lift the paper and tilt it to allow the puddles of paint to meet and mix. The resulting neutrals and mixtures give me new ideas for experimentation.
Left corner puddle: Raw Sienna, Cobalt Violet, Cobalt Turquoise
Top puddle: Quinacridone Fuchsia, Cerumlean, and Aureolin
Right puddle: New Gamboge, Cerulean, and Vermilion
I like all three of these and will use them in an underpainting tomorrow.