Assigning a colour to imorted obj. files that are being used as default material

I am having a problem with assigning a colour to the different meshes that I have on one object. The technique that I have used is the first approach on this site. Is it possible to export a simulation (animation) from Blender to Unity?

So what I would like to do is the following. I have about 107 meshes that are different frames from my shape key animation of my blender model. What I would like to have is that the first mesh will be bright green and up to the 40th mesh the colour turns to be white /greyish…

the best would be if I could assign every mesh by hand a colour, however they are all default materials. And if I assign the object a colour, the whole “animation” is going to be in that colour

Well, I cant assign proper materials and colours in blender since I am exporting it which shape keys ( that is the only way I found to animate a shrinking object in unity)
Thats why I have to do this “stupid” way and therefore I am stuck at my current problem.
I am not working in blender anymore though, so I dont think it is a blender problem.

I will have a look at the unity’s animator tomorrow morning.

Thank you for the tip already.