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