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