Find the Exact Value of the Expression $\sin 255 ^ { \circ } \cos 15 ^ { \circ } - \cos 255 ^ { \circ } \sin 15 ^ { \circ }$

Multiple Choice

Find the exact value of the expression.
- $\sin 255 ^ { \circ } \cos 15 ^ { \circ } - \cos 255 ^ { \circ } \sin 15 ^ { \circ }$

A) $- \frac { \sqrt { 3 } } { 2 }$
B) $- \frac { 17 } { 4 }$
C) $- \frac { 1 } { 2 }$
D) $\frac { \sqrt { 3 } } { 2 }$