Odb abnormal size

Today I followed successfully the steps here reported to link rather than embed images in a odb database.
But I have two problems yet:
1- Although the mysql database is considerably less sized (from 400kb, when I had the blob field to the actual 50kb, with images linked) the odb file size has grown abnormally (from 780kb to 2,2 mb, and every time I do some modification it grows). I don’t undestand why…

Now the size is passed from 2,2 mb to 2,4mb, without adding any new linked image, only with a minor change.

2- The images now linked are black and white in the database, while the original is coloured: why? When the image was a blob field it was coloured.

I fixed so:
1- creating a copy of the file
2- deleting the forms
3- rebuiding the forms.

So I have solved both the problems: the size and the black and white!