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