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