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