To reflect the point \( C(-1, 6) \) over the \( y \)-axis, you will change the sign of the \( x \)-coordinate while the \( y \)-coordinate remains the same.
The reflection of point \( C \) over the \( y \)-axis is calculated as follows:
\[ C' = (x', y) = (-(-1), 6) = (1, 6) \]
So, the coordinates of \( C' \) are:
\[ C' = (1, 6) \]