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