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