So you see it isn't absolutely necessary to follow a theme. Okay, there is a theme going on here, the flowers; but the colors are so very different. I would probably use the "flowers" page as a opening page for any book I may make then follow through with the same colors used in the "wedding" pages for the rest. Possibly using the same colors and flowers in the "flowers" page to conclude the book with a signature page.
When it comes to using colors and themes, it really is up to you.
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