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