Create poolball patterns with LEDs on snooker (pool / billiards) table
Black, when it comes to lighting, is the absence of light, so any LED that's not powered will do. Brown is best achieved using a combination of red, green and blue (R90,G80,B60 for example), since no "brown" discrete LED exists. You might drive an amber or yellow LED very dimly to get a sort of brown color.

Filters, or gels in the lighting industry, alter transmitted color by blocking others. Generally they are placed over a white light, so you could use white LEDs and place brown colored gels over them if you can't control the RGB components separately.

For black, just paint a circle black. You can't produce "black" light, unless you mean "blacklight" which is a common name for ultraviolet in the special effects industry. Such LEDs are usually around 395 nm wavelength and can make some phosphorescent pigments and inks appear to glow.