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