Bug (Case 1201922) Colors render differently between 2019.2 and 2019.3

Hi,

In one of my assets, I use GUI.Box to draw inside a tool window. The color of the drawn box is different when using 2019.3, it is darker. Did anyone notice the same issue? Is there a fix for this, or at least some formula to get a color equivalent to the one rendred in Unity pre-2019.3?

Here is how this test code is rendred in Unity pre-2019.3

and how the same code is rendred in Unity 2019.3


and here is the code used in the test

Code (CSharp):

1.     public class CGGraph : EditorWindow
2.     {
3.  
4.         internal static CGGraph Open()
5.         {
6.             return GetWindow<CGGraph>();
7.         }
8.  
9.         void OnGUI()
10.         {
11.             float grayLevel = 0.5f;
12.             GUI.backgroundColor = new Color(grayLevel, grayLevel, grayLevel, 1);
13.             GUI.Box(new Rect(0, 0, 500, 500), "Test");
14.         }
15.     }