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