depending on the version of ae you have, there are some tips for using swatches in ae here:
https://helpx.adobe.com/after-effects/using/color-basics.html#color_correction_color_grading_and_color_adjustment
scroll half way down the page to the ‘using adobe color swatches’ section.
if you are using an older version of ae that doesn’t have kuler or color themes, there are a few workarounds you can try.
create a new project, create a new comp, add a solid in the color that you want to save for each color that you want to save (you might even name the solids something meaningful). then delete the comp and save the project as something meaningful. you can then import that project and the solids will come with it and you can then use any color picker to pick colors from those solids project window.
another way would be to add color picker effect controls to a null, set the colors as needed and save them as an effect preset to recall when needed and use a color picker to choose from those colors as needed.
or you could do that same technique but with the circle effect to put several colored circles on a layer to use as a palette to choose from in in the viewer rather than the timeline…
Kevin Camp
Art Director
KCPQ, KZJO & KRCW