First open Minecraft's data directory.

If you don't know how to do this, this screenshot will help you.
[![][1]][1]

Go to versions/The version you use

Open it with WinRar (or any JAR viewer)

Navigate to `assets/minecraft/textures/gui`

Open `icons.png` with an image editor.

You should see this:

[![][2]][2]

Paint them with red brush.

That's all! Save it and restart MC.


  [1]: https://i.sstatic.net/ed19O.png
  [2]: https://i.sstatic.net/08FaW.png