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