The color of your brownies is going to depend largely on the quality of the matcha you use. I used ceremonial grade matcha, which is premium matcha that's intended for drinking. It tends to have a much more vibrant green color than culinary matcha tends to have a brownish tint and more muted color. Matcha also discolors as it oxidizes, so if you want a bright green color, make sure you are using the freshest matcha possible.