A room designed by Jill Goldberg of Hudson Interior Designs. (Michael J Lee)

Designers today often judge a book by its color.

On shelves throughout the land, books are being organized not by topic or author but by the color of their spines. Color-blocking books is a design trend that began a dozen years ago at hotels and in design magazines but continues to grow in popularity. Although it’s a bit of a hot potato in the design world, it’s a popular topic on blogs and on Pinterest. DIYers stalk estate sales for old books, peeling off the jackets to see what color hides underneath.

The demand has spawned a host of online businesses that will sell you a shelf’s worth of black books for a library or a row of tangerine books for a sun room. One designer recently contacted BooksbytheFoot.com looking for 30 feet of robin’s egg blue books.

Chuck Roberts, president of Wonder Book, a Frederick company that buys and sells books and also owns BooksbytheFoot.com, says the color-coded book business is thriving. “We had many books that nobody would buy to read. This re-purposes books we can’t sell for reading or collecting. This gives a lot of books one more chance; many would otherwise be sent to a pulper, who takes paper and recycles it.”

BooksbytheFoot.com offers volumes in more than 30 styles. (Books by the Foot)

Roberts says prices vary based on supply and demand. Because black is the most common color, it costs about $12.99 a foot (about $1.10 per book). Gray, a popular color for interiors, runs about $69.99 a foot. Roberts says lime green, sea foam and pink are more difficult colors to stock in bulk.

Choosing the color of the book is part of publishers’ design process. “For the most part, we pick our cover color from a color in the jacket design,” says Suet Chong, a senior design manager at HarperCollins Publishers. “The most common colors are blues, greens and blacks.” But she says some colors are specifically requested by the author, such as the former Playboy Bunny who insisted on hot pink for her memoir.

Nancy Martin started selling color-coded books on her Etsy site Decades of Vintage about a year ago. Her clients are designers, homeowners, theater producers, stylists and wedding designers. “I grew up around books. We always had old books around that were pretty,” she says. Martin says her most popular sellers are blue, green and turquoise. Red is the easiest to find and the hardest to sell. “It’s an easy way to introduce color into a room without making bold, long-lasting decisions.”

Books sorted by color, some from Decades of Vintage, adorn a Bethesda family room. (Bill O’Leary/The Washington Post)

One hotel chain told Roberts they wanted red books for all their presidential and ambassador suites. Martin says: “I made a joke. ‘If someone spends $400 a night, and they see a book they want, they might take it with them.’ But it turns out that would not be possible. They were gluing them onto the shelves.”

The books by color idea gets mixed reviews in the design community.

A toddler bedroom by Lucy McLintic of www.fourwallsandaroof.com. (Lucy McLintic)

“It’s definitely a trend that can work in some interiors, like kids’ rooms,” says Joe Ireland, a Washington designer. “For a sophisticated library or living room, it’s a bit gimmicky.”

Bethesda designer Kelley Proxmire just arranged bookshelves for a client’s home office in Falls Church. “We took off the covers and organized them according to the spines.” says Proxmire. “The client just loves color.” The pink, black, yellow, white and green books are grouped separately.

Kelley Proxmire arranged books in a home office in Falls Church by colors to coordinate with the wall colors and furnishings. (Kip Dawkins)

“Personally I prefer my books to be more organized by subject or by author so it’s easy for me to find the book that I need,” Charles Almonte, a Silver Spring designer, wrote in an e-mail.

And then there are those who see books as more than accessories. “The books in your home tell the story of who you are and where you will go,” Boyds designer Lynni Megginson wrote in an e-mail. “Why try to color-coordinate something so wonderful?”