Luida alternata usually reaches 20 cm from arm to arm but some may increase to a diameter of 40 cm. Its dorsal side is white or cream-colored with bands of dark green, purple, black or brown scattered on it. Its ventral surface is yellow with bright orange tube feet. They have five straplike arms fringed with slender spines. They appear fragile with the rows of paxillae irregularly arranged. The paxillae near the arm margins are larger than the midline and they hold a single long, pointed erect spine surrounded by small spinelets.