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