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