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