The word discolouring is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 21
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (44 words)
closing, codings, codling, coiling, colours, condors, cooling, cording, cordons, corndog, crinoid, curling, cursing, dilogun, dooring, dousing, dulcing, gluonic, grounds, incisor, indigos, indoors, inuloid, loosing, lousing, nordics, origins, ridings, roiling, rousing, rulings, scoring, sidling, silicon, sirloin, slicing, sliding, soiling, soloing, soricid, souring, unclogs, uncoils, uncords