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