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