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