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