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