Planted from red sunflower packet and got all yellow!?

I have been trying to figure out the genetics of sunflowers. Last year, I bought a packet of red sunflower seeds and planted them, but they all came out to be yellow! After the season, they dropped seeds, and I had hundreds of seedlings sprout this year. I selected the darkest purple seedlings from the F2 generation. They grew with purple stems and veins, but when they all bloomed they were yellow again! Some light yellow, some dark yellow. I heard Red was dominant in sunflower genetics, so I'm wondering if an explaination is that maybe the original parent plants could have been pollinated by yellow sunflowers. After seeing the dark purple veins and stems with yellow flowers, I thought red was recessive, but people are saying it's dominant, so I'm confused. I am mainly wondering though if the seeds are true to the respective parent plant or if a plant can throw different genes in each seed and to what varying extent. Also can it both self pollinat and be pollinated by another color? Thanks.