The color of particles in the viewport.
By default, the color is not used for rendering unless you are using a shader that is especially written to use this attribute.
Otherwise, you can get the Color attribute in a render tree using a Color Attribute shader.
This attribute is available to be defined on points of objects other than point clouds, but it isn't used in those cases.
The Color attribute is used in a number of compounds, including Modify Particle Color, Randomize Color, Randomize Color, Turbulize Color by Gradient, and Get Vertex Color Value.
You can quickly get and set the Color attribute for particles with the Get Particle Color and Set Particle Color compounds.