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