If we do not want to use a built-in style, we can always use a custom style. The Delphi installation comes with a number of custom styles. In Delphi 10.2 on Windows 10, FireMonkey custom styles are installed into the C:\Users\Public\Documents\Embarcadero\Studio\19.0\Styles directory. FireMonkey styles are files with the *.style extension. If we preview a FireMonkey style file with a text viewer, we will see that its content looks very much like a form file that we design with Form Designer inside the IDE.
It is good practice not to put non-visual components such as stylebooks directly on the form, but on a dedicated data module instead. Select File | New | Other from the main menu. In the New Items dialogs, select the Delphi Files category and choose to add a new Data Module to the project:
Save the unit as uDMStyles. Change...