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