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