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)(14,31)(15,19)(16,23)(17,29)(18,28)(21,36)(22,33)(25,34)(27,32)(30,40)(35,39)(37,38) involution — undirected(2,6)(7,8)(9,11,15,23)(10,16,19,20)(12,14,22,28)(13,21,30,37)(17,34,35,32)(18,33,31,24)(25,29,27,39)(26,38,40,36)(1,3,5,4)(2,7,6,8)(9,12,14,23,15,22,28,11)(10,16,18,24,19,20,31,33)(13,27,29,21,30,25,39,37)(17,34,26,36,35,32,40,38)(1,4,5,3)(2,8,6,7)(9,13,28,39,15,30,14,29)(10,17,31,40,19,35,18,26)(11,21,22,27,23,37,12,25)(16,32,33,36,20,34,24,38)(2,6)(7,8)(9,14,15,28)(10,18,19,31)(11,22,23,12)(13,29,30,39)(16,33,20,24)(17,26,35,40)(21,27,37,25)(32,36,34,38)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.