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