xvmult and green lines

Hello,

I'm performing mvpart analysis, I've chosen to interactively pick the tree
(xv="pick")  and to do multiple cross-validation (xvmult=10). On the plot x-val
relative error=f(cp/size of the tree) there are some green lines, which didn't
appear during normal cross-validation. What do they depict?

thanks in advance for help
Agnieszka