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