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