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