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