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)(11,18)(12,26)(13,28)(14,22)(15,21)(16,20)(17,25)(19,31)(23,37)(24,33)(27,32)(29,36)(30,35)(34,38)(39,40) involution — undirected(2,5)(6,8)(9,11)(10,17)(12,16)(13,23)(14,24)(15,25)(18,21)(19,34)(20,33)(22,26)(27,31)(28,40)(29,38)(30,39)(32,36)(35,37) involution — undirected(1,3,4,7)(2,6,5,8)(9,12,14,25,15,24,16,11)(10,18,20,33,21,17,22,26)(13,27,29,39,30,38,31,23)(19,34,35,40,36,32,28,37)(9,13,14,29,15,30,16,31)(10,19,20,35,21,36,22,28)(11,23,12,27,25,39,24,38)(17,32,26,37,18,34,33,40)(2,5)(6,8)(9,14,15,16)(10,20,21,22)(11,24,25,12)(13,29,30,31)(17,33,18,26)(19,35,36,28)(23,38,39,27)(32,40,34,37)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.