In MetroLight/Light theme I see #If and #Endif lines as dark grey, the excluded lines inside light grey and normal code as black. Maybe it's your display settings?
However in the Themes folder you can edit the Light.vssettings files
The #If and #Endif lines format is this entry
<Item Name="Preprocessor Keyword" Foreground="0x00333333" Background="0x02000000" BoldFont="No"/>
The excluded lines format is this entry
<Item Name="Excluded Code" Foreground="0x00555555" Background="0x02000000" BoldFont="No"/>
You can make your own vssettings file if you want to and it will show when you select a theme.