Excerpt from page 5 - Salsa Recipes
Many of these recipes call for a certain variety of hot pepper (though some just give you an idea of what size or color hot pepper to use). But this doesn't mean you have to have that particular variety on hand. Substitute at will and enjoy the variety of flavors. A good rule of thumb is to substitute a hot pepper of the same size as the one called for. Also, reread the descriptions of hot peppers beginning on page 3 to make sure you aren't introducing more heat than you had in mind!
Another good point to remember is that peppers, even withing the same species, may vary in heat. So unless you have a true tolerance for chiles of any temperature, err on the cool side when estimating how many hot peppers to use in your recipe. You can always spike up the warmth at the end with a little ground cayenne or hot sauce. "Copyright permission by Storey Communications"