If \(\vec a\) & \(\vec b\) are collinear vectors, then they are parallel.
Then, \(\vec b=\lambda\vec a\)
For some scalar \(\lambda\)
If \(\lambda\) = \(\pm1,\) then,
Thus, respective components of \(\vec a \) & \(\vec b\) are proportional.
However the vectors \(\vec a \) & \(\vec b\) can have different directions.