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