Purebred Arabian horses come in many beautiful colors, including bay, chestnut, grey, and black; white; roan; some unusual variations like palomino and sabino pinto, which can be double-registered with the respective "color breed" registry; and a very rare "striped" or brindled color.
While a good horse is never a bad color, some people choose to breed for specific colors. If you would like to do this, it's a good idea to study the available material on equine coat color genetics.
Here are links to some of my favorite websites offering such information:
The study of genetics is fascinating, and mapping of the equine genome has contributed to the creation of various "carrier tests" which can help prevent deadly conditions such as SCID, CA and LFS.
Here are links to some important websites offering information about these conditions, and equine genetics tests that can be purchased to help you make sound breeding decisions:
F.O.A.L. - Fight Off Arabian Lethals http://www.foal.org/index.html Information about the various genetic lethals that can affect Arabian horses, with links to order test kits, and lists of known carriers.
Cornell University http://www.ansci.cornell.edu/brooks/research.html I participated in their recent study of Lavender Foal Syndrome, which resulted in the development of the first LFS carrier test. No, contrary to popular belief, LFS isn't found only, or even predominantly, in Egyptian Arabians! My herd contained two mares who were LFS carriers, and neither had an appreciable amount of Egyptian breeding "close up." I highly recommend getting your breeding stock tested, and NOT breeding carrrier to carrier! Here is a link to an article about the LFS study: http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1000909