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