How to change subtitle size and colour?

I want to make it smaller so, the double-lined ones can fit in the black bar. I remember there was a place where I can change the size and the colour of the subtitle font, but can’t find it today. Where are the settings located now?

Some subtitle types will have limited customization options, as they are graphic-based.

If you use a text-based subtitle format like SRT you should be able to customize everything.