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