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