like if you want to change the font then do something like [font= whatever the font is] and then Size would be[size= whatever the size is like 10 or higher] (Make sure you close all the brackets [] like that.
Same thing with color. so here see if this helps [ size = number ] Your Letters and then [ / size] thats how it should look except without the spaces between everything. I added the spaces so that you could actually see everything without it showing up. Hope this helps

Also theres a more detailed thread thats discussing how to do it, it's title signatures .
DGP~Honey~