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