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