How can I NOT apply a texture to part of the model?

I have a simple 16 x 16 grid to which I apply a single texture. The texture file is divided into four parts - each a different color. By default each square is colored green (upper left part of the file). If you click a square I apply the red portion (upper right part of the file). Now I want to make the square disappear entirely when clicked. I suppose I can use a transparent texture but I was hoping I wouldn't have to so as to avoid loading / reloading two different texture files.

Here is the code I use to update the texture vbo:

  //I don't bother offsetting my changes.  I simply update the 'UVs'
  //array and then copy the entire thing to the floatbuffer.   
  public void updateTexture(int offset)
  {

      //populate the texture buffer
      //fbtex is a floatbuffer (16x16x8 in size). UVs is an array, same size.
      fbtex.put( UVs );
      fbtex.rewind();

      glBindBuffer(GL_ARRAY_BUFFER, vboHandles.get(TEXTURE_IDX)); //the texture data
      glBufferSubData(GL_ARRAY_BUFFER, offset, fbtex);
      fbtex.clear(); //don't need this anymore  
  }

The VBO will contain up to 256 instances of my co-ords for Green:

public float[] UV_0 = { 0.02f,0.02f, 
                        0.02f,0.24f,
                        0.24f,0.24f,
                        0.24f,0.02f};

or less if includes a few of my co-ords for Red:

public float[] UV_1 = { 0.24f,0.02f, 
                        0.48f,0.02f,
                        0.48f,0.24f,
                        0.24f,0.24f};

Is there anything I can do to the VBO data to draw a section invisible? So the objects in the background can be seen for example?

Solution

You can just not render parts of the VBO. Normally you draw the entire data with something like

glDrawArrays(GL_TRIANGLES, 0, numElements);

glDrawArrays takes a first and count parameter which you can use to render only a part of the VBO. So if you wanted to not render some data, you would render all data before and then after this data in two draw calls.