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