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