Cauliflower is covered with several layers of green leaves attached to the stem. The small, tender, inner leaves, which are yellow-green in color, are edible. Cauliflower is usually white, but some varieties are purplish in color (they turn green during cooking). Purple cauliflower is very close to broccoli; it cooks more quickly than white cauliflower and has a milder flavor.
Read more: http://www.answers.com/topic/cauliflower#ixzz1eED3W9oa