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