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