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