I think it's because we used to relate love with our heart. And as the color of heart is red. So love is also symbolizes as red.
Other popular belief is, as Red is also a symbol of joy and celebration. It more likely goes with love.
Thought different culture symbolizes love with different color. But mostly red is the color to express love.
From my opinion, as red is a vibrant colors and don't fade away quickly. It is also a good reason to use red as the color of love.
But there are some other colors too as 'baby pink ' or 'sky blue' symbolizes love in some society and we can see it in different products as well.
But what express love most without the color of our heart. With out heart ( I would say brain) there would be no love.
Stay blessed. Keep loving.
Red is a warm and powerful color. It is the color of power, but also that of blood. The red depicts both declarations of war and declarations of love. In the language of flowers, red is associated with love, eroticism and passion. A bouquet of red flowers is offered in an intimate setting, to make a declaration of love, to share a love at first sight or simply to express one's feelings. The iconic color of Valentine's Day, the red is suitable for other occasions: a birthday or congratulations.
However, it is not recommended in a professional context or during ceremonies such as marriage and bereavement.
I think Red represents eternity.
Like the red color of blood flowing in every vein of our body. Fused together in our body. We should give what we have to fight for our love for someone.