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