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