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