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