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