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