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