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