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