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