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