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