This is an example of co-dominance. In your example red is the recessive trait, yellow is dominant and orange is co-dominant meaning that both the red and yellow genes are showing equal expression rather than one being dominant and one being recessive.
Your genotypes are Ff, fF, FF and ff.
Ff and fF are co-dominant. They display both the recessive AND dominant traits and are orange in color.
If you cross two orange flowers you would get the following:
This means 1/4 of the flowers will be red, 1/4 will be yellow and 1/2 will be orange.