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