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