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