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