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