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