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