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