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