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)(25,26,32,36,31,35,30,34)(27,28,37,38,29,33,39,40)(1,2)(3,6)(4,5)(7,8)(10,14)(12,19)(15,20)(18,23)(25,27)(26,33)(28,35)(29,31)(30,39)(32,37)(34,38)(36,40) involution — undirected(2,5)(3,7)(9,11)(10,15)(12,18)(13,17)(14,20)(16,22)(19,23)(21,24)(25,28,31,33)(26,27,35,29)(30,38,32,40)(34,37,36,39)(1,3,4,7)(2,6,5,8)(10,14)(11,17)(16,21)(18,23)(25,29,31,27)(26,28,35,33)(30,37,32,39)(34,40,36,38)(2,5)(6,8)(9,12,13,19)(10,16,14,21)(11,18,17,23)(15,22,20,24)(25,30,31,32)(26,34,35,36)(27,37,29,39)(28,38,33,40)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.