I agree with J Cook that Gateway's flourescent yellow feathers are really bright. I use them and they are easy to see when I have to look for an arrow. Also the nock color is important as sometimes in grass, when an arrow is along the ground, the only point of the arrow you see is the nock.
I have used red and yellow fleatching for over 50 years and used to dip my woods in red or crown dip my aluminums in red. Red is a color almost everybody avoids because of the color of blood, fall sumac leaves, etc, but when used with a bright nock and a flourescent yellow feather, the flourescent yellow makes them easy to see, so due to Gateways flourescent yellow, I still can use the red as the second color in my fletchings.