Color Picker questions allow the submitter to select a color. You can give them a choice from some preset swatches and/or let them choose a custom color themselves.
To change the swatches available for a Color Picker question:
Hover over the question in the editor, then click the cogwheel icon to the right to configure it.
Scroll down to the "Swatches" setting.
You can delete any existing swatches by clicking on them individually.
Select the color for a new swatch. Do to this, you can:
#symbol. Three-character shorthand is allowed, so both
#FFFwould be accepted.
RGB(256, 256, 256).
Once you're happy with the color, click the "Add swatch" button.
If you'd like to limit the options to specific swatches rather than letting the submitter choose a custom color, toggle on "Allow swatches only."
Alternatively, you could delete all of the swatches if you only want to show the custom color slider and canvas with no preset options.