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