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