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