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