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)(19,20)(21,32)(24,30)(26,27)(35,40)(36,37) involution — undirected(1,2)(3,6)(4,5)(7,8)(9,10,14,17,16,21,15,32)(11,23,26,34,27,38,22,18)(12,29,13,20,31,33,28,19)(24,36,39,40,30,35,25,37)(2,5)(6,7)(9,11,15,22,16,27,14,26)(10,18,17,23,21,34,32,38)(12,30,28,39,31,24,13,25)(19,36,29,40,20,35,33,37)(1,3,4,8)(2,6,5,7)(9,12,14,13,16,31,15,28)(10,19,32,33,21,20,17,29)(11,24,26,39,27,30,22,25)(18,35,38,40,34,36,23,37)(9,13,15,12,16,28,14,31)(10,20,32,29,21,19,17,33)(11,25,22,30,27,39,26,24)(18,35,38,40,34,36,23,37)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.