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