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