How do I color / texture a 3d object dynamically ?

I have a 3D model, composed of triangles. What I want to do is, given a point near to the model, I would like to color the model (triangles) to another color, say blue.

Right now, I have a bounding sphere about the model, and when the collision occurs, I just want to approximately color the portions of model from where the collision occurred.

Also, for now I am using VBOs to render the model (with only vertex position information in there…thus its a wireframe as of now)

Can someone please suggest me something that I can use and make this happen ?