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