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