[Splat]

Text toolbar, not text tool. That'll let you change font and size.
While we're on the matter, could you delete the dialogue from previous frames when you start a new one?

Also, if you click on the icon just above the pencil in paint (the one that looks a little like a dagger) and then click on the colour on the picture that you want it'll select that colour. So click on the dagger, then click on my grey background, and you'll have that colour. It's very simple.

Or if you click 'colours' on the toolbar at the top, then 'edit colours', then on the box that appears 'define custom colours' you'll be able to pick any colour known to mankind.