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