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