Dark Green leaves as well as light green. Normal? Cause?

[bibsoconner]

Check out these pictures. Recently my White Widow plant has dark green leaves. Not unhealthy looking by any means. Just seems odd that it has two different shades of green. Any ideas?

 

[bibsoconner]

Check out these pictures. Recently my White Widow plant has dark green leaves. Not unhealthy looking by any means. Just seems odd that it has two different shades of green. Any ideas?

Sorry, this is Cream & Cheese CBD 1:1 Feminised Seeds from Seedsman, not White Widow. I need to stop smoking and start growing or I'm going to lose crop due to careless mistakes! However, the question remains: why the combo of dark and light leaves?