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