Oakleaf hydrangea has two colors of green leaf
Q: What are your thoughts about these unusual leaves?
A: Wow, neat pictures! This is called a chimera.
Basically, the bud that produced one of these leaves had a mutation in its cells, causing some of those cells to grow but not produce chlorophyll.
Many common variegated plants originally came from chimeras: variegated dogwood, variegated vinca vine, ‘Burgundy Glow’ ajuga, variegated hosta, variegated hydrangea, etc.
Some variegated plants are attractive and are propagated by growers and sold at nurseries. Others have leaves that are so lacking in chlorophyll that the plant never prospers.
If you like adventure, try to root cuttings that bear these chimeric leaves and see if you can get more.