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