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)(11,17)(12,14)(13,16)(15,18)(19,24)(20,22)(21,23)(25,26)(27,33)(28,31)(29,34)(30,32)(35,40)(36,38)(37,39)(1,2)(3,5)(4,6)(7,8)(9,11)(10,15)(12,17)(13,21)(14,18)(16,24)(19,22)(20,23)(25,27,30,28)(26,31,32,33)(29,35,37,36)(34,38,39,40)(10,12)(11,18)(16,20)(19,21)(26,32)(31,33)(34,39)(38,40) involution — undirected(1,3,4,7)(2,5,6,8)(9,11)(10,15)(12,17)(13,19)(14,18)(16,23)(20,24)(21,22)(25,26)(27,31)(28,33)(29,34)(30,32)(35,38)(36,40)(37,39)(9,12,14,10)(11,17,18,15)(13,16,22,20)(19,23,21,24)(25,28,30,27)(26,33,32,31)(29,36,37,35)(34,40,39,38)(9,13,14,22)(10,16,12,20)(11,19,18,21)(15,23,17,24)(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.