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