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