coralline algae will come in many colors including orange... but some of your sponges can be orange in color and can be confused for coralline algae aswell.
As you might already know lighting plays a big role regarding coralline algae, so some species grow way better in higher intensities lights and others grow better in low intensities. and really light wavelength can make a difference as well. that's why you'll see coralline algae covering the sides of rock better because they don't get as much light and you'll see different colored corraline growing in shaded like beneath overhangs.