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