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