Two More Paintings on Values and Secondary Colors

Here's my third oil painting called 'Secondary Colors'.  This represents the purple, green, and orange colors that are created by mixing the primary colors of red, yellow, and blue.  I then mixed the purple, green, and orange colors to create the background colors.  I also used some titanium white to create the lighter colors.  I have to wait a few days for this painting to dry before I can finish it.

My second painting represents another take on values, but in the color blue.  I used Ultramarine Blue and Titanium White to create the values.  Before I finish this painting, I have to wait a few more days for the painting to dry.  

I'm trying to figure out if I should paint the background first and let it thoroughly dry and then paint the objects.  Currently, I'm painting the objects first and then painting the background.  This method makes it harder to paint in between the objects.