Set color for the whole mesh but not every vertex

I want to optimize size of vertex buffer. Currently my layout for VBO is:

x y | r g b a
It's consumed by shader like this:

struct VertexInput {
   @location(0) position: vec2<f32>,
   @location(1) color: vec4<f32>,
}

And I'm storing mesh in buffer like this: |Mesh1_____|Mesh2____|LargeMesh3_|, because my meshes are dynamic. It's being rendered in one drawCall.

I want to reduce sent data to GPU by setting color for every mesh, not every vertex. How can I achive it?