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