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