How to distinguish between Lavender & Blue
It is very easy to identify a Lavender bird by looking at the main tail feathers. If the outer-side feather shaft is pale & the inner feather shaft is dark, it is more than likely Lavender. The inner feather-web also has a darker iridescent-like sheen, which extends outwards from the shaft
http://www.edelras.nl/belgians/colour.htm
I started with Lavenders... very easy to tell the difference.
Spend nearly 3 years working with them. Have photos but they would be too small to post.