tarev: Give them lots of bright light and the leaf colors should become more vivid. I can't tell from your photos for sure but the cultivar you have may possibly be 'Batik'. I used to have a couple of them and I think I remember the leaves on Batik doing that ... don't know why it happens but it's possibly just a characteristic of that particular cultivar.
I will be very interested to hear how they do in your area during the summer months but I'd think as long as they get sufficient water and are kept from direct, burning sun they will thrive! I've always heard that Codiaeum do not like fertilizer so I've never fed mine.
