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