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