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