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