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