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