Removing this line on tabpage border

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C#

tabs

TabControl

I can't figure out a way to remove this area around the TabPage, I painted it in red so that it is easy to see.(Picture 1)

My issue though is when I change it back to the background color, I lose the tab selector(Blue Highlighter) when I have a nested Tabcontrol and it goes under that red highlighted area. (Picture2)

I am using the iTalk Tab Controller and i know it is a bit outdated however it fits my needs. [C#] iTalk Theme - C# - Pastebin.com[^]. The code that changes color is "_Graphics.Clear(Color.FromArgb(R,G,B))" around line 4326

I would prefer to remove the marked area or make transparent, I don't like having the space between Main Tabs and nested tabs.

Picture 1 Below:
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Picture 2 Below:
Difference between the 2 blue markers from main tab to nested tabs
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-Thanks In Advance

What I have tried:

Changing the color to Color.Transparent Doesn't Help.