Do not be afraid, this is a well-known limitation of WiX. In principle, the checkbox and radio buttons do not support transparency, so by default there will be a gray background.
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, checkbox:
<Control Id="LaunchCheckBox" Type="CheckBox" X="134" Y="126" Width="10" Height="10" Property="LAUNCHAPPONEXIT" CheckBoxValue="1" Text=" " >
<Condition Action="show">NOT Installed</Condition>
</Control>
<Control Id="LaunchText" Type="Text" X="149" Y="126" Width="170" Height="17" Text="Launch $(var.ProductNameForDisplay)" Transparent="yes" >
<Condition Action="show">NOT Installed</Condition>
</Control>