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