Well, Iīve searched the web for hours

and found another few posts, there was an reply like: (but I guess itīs rather impossible to change)
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Go to this key in the Registry -
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ThemeManager
Double-click on 'DllName' in the right-hand pane and change the value to your chosen visual style in C:\WINDOWS\Resources\Themes ....
After doing that, go to this key in the Registry -
HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\ThemeManager
Change the same 'DllName' value to your chosen visual style as show before but also double-click & change 'ColorName' to the sub-style you are using e.g. 'Homestead' for Luna Olive or 'NormalColor' for a visual style's default theme ....
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but the trick didnīt work.
Iīve read and noticed, that if the style is in windows classic mode, after youīve logged out, windows is switching to newer optic (and show the blue screen even with "olive" or "silver" activated). Iīve found a few entries for luna in the reg (*.msstyles,*.theme), but donīt know by what to replace it?