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