There are a number of differences between these two small birds.
Firstly the Great tit has a black stripe going down its breast to
its tail and the Blue tit only has a small black incomplete stripe.
The great tit also has a black cap and the Blue tit has a blue cap.
The Blue tit also has more white on its face than the great tit.
And a subtle difference is the Great tit is slightly larger than
the Blue tit.
The great tit is also different from the Blue tit.