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