Changing lettuce leaf color

[Leenstar]

I had Forellenschuss lettuce (green with red-purple speckles) in a cold frame and transplanted a couple of specimens to another bed so I could save indivual seed varieties (all my lettuce seeds have been a big mix of all my varieties).

I am now about two weeks post transplant and the plants are healthy but the usually green Forellenschuss has converted almost entirely to the red-purple color.

I assume there either an abundance of a mineral or an abscense and figured I would inquire with all you resident experts for some insight/explanation.

It is a new bed in clay soil with some but probably inadequate amendment.

Attachments:

[steev]

Could it just be a response to stronger light?

[flowerpower]

I wonder if it is related to the soil temp. The soil in that bed is probably a lot cooler than the cold frame.

[robertb]

That's usually a response to light levels.