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