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)(11,13)(12,20)(14,15)(16,18)(17,21)(19,24)(22,23)(2,3)(6,7)(10,15)(11,18)(12,21)(23,24)(25,26)(27,32)(28,29)(30,31)(33,38)(34,40)(35,37)(36,39) involution — undirected(1,3,5,2)(4,7,8,6)(10,15)(13,16)(17,20)(23,24)(26,31)(29,33)(32,39)(35,40)(1,4,5,8)(2,6,3,7)(9,11)(10,16)(12,22)(13,15)(14,18)(17,23)(19,21)(20,24)(25,27)(26,32)(28,37)(29,35)(30,36)(31,39)(33,40)(34,38)(9,12,14,21)(10,17,15,20)(11,19,18,22)(13,23,16,24)(25,28)(26,33)(27,34)(29,31)(30,38)(32,35)(36,37)(39,40)(9,13,14,16)(10,11,15,18)(12,23,21,24)(17,19,20,22)(25,29,30,33)(26,28,31,38)(27,35,36,40)(32,37,39,34)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.