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)(27,33)(28,39)(29,35)(30,36)(31,40)(32,37)(34,38) 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)(25,27,32,38)(26,33,37,34)(28,30,29,31)(35,40,39,36)(9,12,13,20)(10,15,16,24)(11,17,18,19)(14,21,22,23)(25,28,32,29)(26,34,37,33)(27,30,38,31)(35,40,39,36)(1,4,5,3)(2,6,7,8)(11,18)(14,22)(17,19)(21,23)(25,29,32,28)(26,35,37,39)(27,30,38,31)(33,36,34,40)(10,16)(14,22)(15,24)(21,23)(25,30,32,31)(26,36,37,40)(27,28,38,29)(33,39,34,35)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.