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