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