If the red X on the flag of the Siberian Whites annoys you as much as it annoys me, here is a version of Kolchak's flag without it. Look in the image below at the blue circles:
As you can see I have not edited the big flag image in the upper left. Consider the red still in that flag as:
a) a symbol of Kolchak's consideration for the blood spilled in the defense of the anti-Bolshevik cause;
b) a result of my lack of skill with graphics software, which led me to the conclusion I shouldn't mess with it
Unzip the attached archive. It will create a folder with the same name as the archive. Inside it you will find a folder called "Graphics". Copy it and then go into the folder where you have installed RUS -> the "RUS" folder. You should be looking at a list of folders: "Aliases", "Events", "Fonts", etc. Paste the "Graphics" folder there and say yes to the "overwrite" questions.
Also attached is the original flag, should you want to come back to it.