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