How to make a GUI Texture (image) transparent?

Hello! I have a simple image made in GIMP that is gradient, green to white. I loaded this image into my code through the editor, and I need to edit the entire images’ transparency.

My code to load it in is simple:

public Texture GPgreen;

I’ve assigned my image to that slot in the editor, and need to affect the whole things transparency. It is drawn as follows:

GUI.DrawTexture(new Rect(commonLeft + padding, commonTop + padding, healthBarLength
		                         ,healthBarHeight), tex1);

Any help is greatly appreciated.
Thank you!

Define your GUI color in the first line of you OnGUI function.

GUI.color = new Color32(255, 255, 255, 100);

When you click on your Texture in the project panel, look in the inspector and change the Texture Type to GUI, you might also have to change the format to truecolor.