The mathtools package has a centered colon, \vcentcolon, which is used to display the definition symbol := correctly.
However when using the fourier package, I get the following output

from
$:\vcentcolon=$
where I have added a normal colon as comparison.
The second colon is slightly adjusted, but not entirely centered upon the =. How do I get \vcentcolon: right?

:that doesn't look right to me. Why not write\vcentcolon\vcentcolon=? – A.Ellett Jul 22 '13 at 15:00$\vcentcolon=$to be adjusted correctly. – Deniz Jul 22 '13 at 15:13