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