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