Listing my ideas....

... these books are a few examples :

• Claudia Mair Burney Zora and Nicky 
•  Patricia Haley Blind Faith
•  Michelle Stimpson Boaz Brown 
•  Linda Leigh Hargrove The Making of Isaac Hunt
• Jacquelin Thomas Shades of Gray

I also noticed this series written by Marilynn Griffith Shades of Styles Which focuses on four women of different backgrounds. I am not sure if any of the romantic relationships are about blending but they did look interesting.