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