They sometimes describe its color as white, sometimes as blue. Perhaps, we should better say that the pill is bluish white. Oval, with one side scored. "WATSON 540" index is debossed on the other side of the pill (letters above figures). As for the appearance, that seems to be all.
Now, active ingredients. Due to the fact, that Watson 540 pill is, in fact, generic Vicodin 10/500, each Watson 540 contains 10 mg hydrocodone bitartrate and 500 mg acetaminophen. The pill can as well be listed as generic Lortab or Norco (all the names are trade name variations for the same medicine).
A fact should be mentioned that generic versions of Vicodin 10/500 are distributed by other manufacturers, too. Along with Watson 540, the same strengths of hydrocodone and APAP can be found, e.g., in M363 pills manufactured by Mallinckrodt Pharms.