Officially, No, but many consider it to be because the power
that the British exercised over Iraq during its mandate-period
resembles colonization.
Iraq was part of the Mandate System and as such, the British
expended a great deal of manpower to "modernize" and "control" the
country. Officially, however, mandates were not colonies in that a
mandate has the future purpose of becoming a realized independent
state. A colony does not have such a purpose. The Mandate of Iraq
was maintained from 1919 until 1921 when the British transferred
authority to King Faisal I. However, the British interfered often
with Iraqi policy and maintained boots on the ground until
1954.