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