To start a new custom theme you need to. I used
test as a name anywhere you see
test as a name that's where you put
your theme name.
#1 Go to C/Windows/Resources/Themes
Get a copy of the Aero folder and aero.theme file.

# 2 Right click & rename the 2 (Screenshot below step # 2)

The Aero folder needs renamed to
your theme name
The Aero.theme file needs renamed to
your theme name.theme
After (Screenshot below)

# 3 The
your theme name.theme file needs opened up with notepad and renamed. (Screenshot below step # 3)

# 4 Delete @%SystemRoot%\System32\themeui.dll,-2013 & replace with
your theme name Look at screenshot. This is the top of notepad
(Screenshot below step # 4)

After (Screenshot below)

# 5 Delete Aero\Aero & replace with
your theme name
Look at screenshot this is the bottom of notepad.
your theme name\your theme name
(Screenshot below step # 5)

After (Screenshot below)

# 6 Open
your theme name folder you need to rename the Aero.msstyle inside it.

to
your theme name.msstyle
(Screenshot below step # 6)

After (Screenshot below)

# 7 Then open the en-US folder. (Screenshot below step # 7)
# 8 Rename the aero.msstyles.mui file to
your theme name.msstyles.mui (Screenshot below step # 8)

After (Screenshot below)

Edit
your theme name.msstyle & save it
Put all of it in new folder with your theme name & zip it & share with others
Jerry