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