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