This isn't possible right now.  We're trying to strike the right balance between customization and ease-of-use, and we think for now that the best solution is to stick to the proven page templates.

However, we know that some people want the ability to change font colour and size.  If you're one of them, please drop us a line at - if we get enough requests then we'll know we don't have that balance quite right, and we can add this feature.