One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,6,7,5,3,4,8)(9,10)(11,17)(12,24)(13,16)(14,19)(15,20)(18,26)(21,29)(22,36)(23,31)(25,30)(27,34)(28,33)(32,35)(37,40)(38,39)(1,3,4,7,5,2,6,8)(10,16,20,19)(11,21,23,28)(12,25)(17,31)(18,24,34,30)(22,37,38,35)(26,27)(29,33)(1,2,5,3)(4,7,6,8)(9,11,15,23)(10,17,20,31)(12,22,25,38)(13,21,14,28)(16,29,19,33)(18,32,34,40)(24,36,30,39)(26,35,27,37)(1,4,5,6)(2,7,3,8)(9,12,14,27,15,25,13,26)(10,18,16,30,20,34,19,24)(11,22,28,37,23,38,21,35)(17,32,29,39,31,40,33,36)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.