\left.\begin{array}{l}
(17)_{16} = 1 \cdot 16 + 7 = 23 \\
(19)_{16} = 1 \cdot 16 + 9 = 25 \\
(ab)_{16} = 10 \cdot 16 + 11 = 171
\end{array} \right\} \Rightarrow {\rm \#1719ab} = ({\rm R\!:}\ 23, {\rm G\!:}\ 25, {\rm B\!:}\ 171)