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