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