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