I want a dark red and a dark blue for a flag I'm making.
How can I get the colors to be dark instead of coming out pastel?
Red is best made if you colour the icing a dark pink first. You will get a darker red from a pink base than from a white base. For navy blue, I used some sky blue, some violet (I think?), and a dab of black. There is a colour mixing chart on this site somewhere. Also, colours will darken as they sit, so if you can make them a few days in advance, that's ideal. Then, you'll know if you need to add a touch more read to darken it, or if it will be a nice, deep red without adding any more colour. Some people say that Americolor colours work better than Wilton colours.