Red strain among the white

This is the first time I have seen such a completely pink -- and hot pink, at that -- strain of white clover. Normally you may see white clover with some pink tips or pink flowerlets at the base. Seeing this, however, left me grinning for days. While out walking, I saw the white clover getting progressively pinker and pinker until I saw a whole plant that rivaled its red clover neighbors. As I walked further, the pigment disappeared and went back to white.
There is much I don't know about the world. This mystery is a prime example. Is it a mutation? Is it a manifestation of a recessive gene? Is it a cross pollination with the red clover? I don't think it is cross pollination, because the two types (T. repens and T. pratense) have several differences, from leaf shape to flower shape to flavor of nectar (yes, I have sampled them). I didn't sample this hot pink one, though. I don't want to interfere if it is something genetically important.
For the skeptic, here is a sampling of what I saw. First, white clover.

Then more white clover with pink.

And more pink.

Here's a red clover.

Here's the red strain of white clover to give you an idea of size.

To all you backyard naturalists, stay curious!