Invisible image overlay for bars

[TeamFord]

I am trying to make a bar for RAM Usage, and I want it to be this style, with the white only coloring the squares: but I have absolutely no idea how

[balala]

I am trying to make a bar for RAM Usage, and I want it to be this style, with the white only coloring the squares: but I have absolutely no idea how

Recolor the white image to blue, using any tool like Photoshop, Paint.NET, or whatever and save the new image.
Create an Image meter which will show the blue image. Then create a Bar meter, which will use the white image in its BarImage option. Take care to place the two meters in the same position.
If you can't do all this, please post the image first.