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