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