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