One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,6)(3,5,7,8)(9,10,14,15)(11,16,18,13)(12,20,22,17)(19,21,24,23)(25,26,30,27)(28,33,35,31)(29,32,37,34)(36,39,40,38)(1,2)(3,5)(4,6)(7,8)(25,26,30,27)(28,31,35,33)(29,34,37,32)(36,39,40,38)(1,3,4,7)(2,5,6,8)(10,15)(11,18)(17,20)(19,24)(26,27)(28,35)(32,34)(36,40)(9,11)(10,16)(12,19)(13,15)(14,18)(17,23)(20,21)(22,24)(25,27,30,26)(28,33,35,31)(29,34,37,32)(36,39,40,38)(9,12,14,22)(10,17,15,20)(11,19,18,24)(13,21,16,23)(25,28,30,35)(26,31,27,33)(29,36,37,40)(32,38,34,39)(9,13,14,16)(10,11,15,18)(12,21,22,23)(17,19,20,24)(25,29)(26,32)(27,34)(28,36)(30,37)(31,38)(33,39)(35,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.