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