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