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