Don't specify font color.
Don't try to match the font color in the editor to how it looks in the community*.
Don't pick a special font color for emphasis.
Don't do chat logs in different colors for different people.
Don't make announcements that specify colors even if it's a theme and you want it to look pretty.
Not if you want people to read it.
When it goes out onto the reading page, you no longer control the background color. Your color choice looks great on a white or light grey background. How does it look on black? Blue? Orange?
Don't specify font color. Specifying a color overrides the font color choice of the reader. It doesn't override the background color choice. It might be barely noticeable, or it might be unreadable.
Readers have different reasons for picking the background and text colors in their layouts. Sometimes it's aesthetic. Sometimes it's because they have low vision and can't read anything that is smaller or has less contrast. Sometimes it's because they're very color or light sensitive and some colors (such as very bright whites and cyans) give them debilitating migraines.
When you're posting in community space, don't be a jerk.
*When you're posting in your own space, you can control the look of the place, including colors, through your layout and make it look how you want that way. When you change your mind about how you want to have your space look, it's tedious to go back through old entries and change your font color.
[cranky old internet denizen muttering]