They can be in various colours and the main colour to be worried about is green as the Green Brittlestar (Ophiarachna Incrassata) which can grow up to 20" across and can consume fish (including clowns, damsels, and ornamental shrimps.
Common Name(s): Brittlestar
Scientific/Other Name(s) : Ophiarachna sp.
Care Level : Easy
Maximum Size: var.
Minimum Tank Size: none
Reef Safe: yes (except for Ophiarachna Incrassata)
Feeding Requirements: harmless detritus eaters
Temperament / Behavior: Peaceful
As with all other invertibrates the Brittlestar is intollerant to copper and high nitrates in the aquarium.