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