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