Got this idea from reading a fic FlameAlchemist007 wrote. Friendships include:
SanadaxAtobe
KintaroxRyoma
MaruixJirou
YushixKenya
SenrixTezuka
ShusukexYukimura
GakutoxEiji
RenjixSadaharu
Color Friendships of Court
Azure
Gakuto took a look at his azure uniform again, the symbol of Hyotei, when he found Eiji murmuring to himself, "Why is our jersey blue, like that Hyotei group? I want ours to be a good color, like red..."
Bronze
Kenya fingered his bronze medal again, which he have received back at the Nationals. That moment, Yushi finds him and says, "Maybe if I haven't played, Hyotei would've won a medal too."
Cerulean
Yushi stared at the picture again. It was of him and his cousin back in Osaka, swimming in a cerulean pool.
Daffodil
Senri was busy reading his book in the park when he saw Tezuka walking over to a flower field. He only smiled at the buchou and said, "You know, Tezuka, daffodils are Miyuki's favorite flowers…"
Emerald
Shusuke had always wondered where Yukimura had gotten his emerald green headband. He found that out when he discovered him saying, "I had to say, Sanada was very nice to give this me..."
Flame
In retrospect, Sanada and Atobe are fire and ice. Sanada is the flame that moves the team, while Atobe is the cold that stops others dead in their tracks. They are pure opposites, but when combined, they are an unstoppable force.
Gold
One thing Kintaro notices about Ryoma is his gold colored eyes. He thinks it's because of winning so much that a reflection of a gold medal is always in there. Ryoma never corrected him, because he likes the "winning so much" part.
Hazel
Eiji was walking around when he saw Gakuto stuck up a hazelnut tree after jumping too high. Instead of laughing, he got the boy down. After that, Gakuto asked why did his rival helped him, and Eiji answered, "That's what Oishi would do if that happened to me."
Ivory
Tezuka opened the ivory white box and inside was a new racket. When he looked at the card, it said, "This is a thank you gift from me and Miyuki. Thanks for helping her become a good tennis player. - Senri."
Jade
Marui was about to break the jade controller cause someone kept beating him at this fighting game game. As he stormed out, Jirou found him and said, "That was just Ryo. He's mega competitive. Don't ever fight him again."
Khaki
Eiji was wearing his new khaki pants his mom got him when Gakuto ran by complaining of his now ruined jeans. Eiji laughed and said, "Don't worry. I got an extra pair like that at my house."
Lilac
Shusuke took a look at Yukimura's beautiful flower garden and smiled even more. Maybe he should grow more than cactuses. The lilacs are his favorite cause they're gentle, like the both of them.
Mahogany
Jirou woke up from usual sleeping place at a mahogany tree only to find Marui sleeping there too. Instead of screaming like a fanboy at times like this usually, he just wrapped his arms around the boy and fell back to sleep.
Navy
"One question, Kenya. Why did you bleached your hair? I don't like it this way." Yushi asked as his navy blue hair fluttered in the breeze. "Don't you remember, cous? People kept mistaking us as twins." The speedstar replied.
Obsidian
Sadaharu was looking in his selves one day when he found a obsidian black book. He smiled. It was one of Renji's old notebooks, and it contained data of all the opponents they faced when they were a doubles pair.
Platinum
Shusuke had gotten a platinum ring from his mother. As he stared at the shine it made, he wonders if Yukimura had ever gotten a reminder of his friend like this.
Quit
"Sanada, ready to quit this game?" Atobe bragged to the emperor during their tennis match. Sanada only replied with a slight smirk on his face, "Atobe, you're only making me want to finish this game more."
Rose
"So, cous, whatcha reading?" Yushi only groaned at Kenya while reading his new romance novel. "It's called, 'Rose Tears'." The bluenette replied. Kenya then said that book had over fifty chapters (which Yushi thanked god that he didn't waste his money).
Silver
As Sanada grasped the silver medal in his hand, a painful reminder of how he lost the Kanto Tournament to Ryoma, Atobe looked over and said, "At least you don't have your shaven head as a reminder for losing to that brat."
Titanium
Tezuka was looking at his titanium fishing rod again. He fishing with his grandfather at the lake. As Kunikazu was getting ready, Tezuka suddenly found Miyuki and Senri was having picnic not far from there.
Ultramarine
"This is my new Ultramarine Mega Fish Power Juice." Sadaharu introduced his drink. As the other regulars back in fear and disgust, he made a note to thank Renji for helping him with making the latest batch.
Vanilla
As Jirou licked his vanilla ice cream, Marui suddenly entered the shop. As an eager fan of the red head, Jirou offered Marui his ice cream. Not passing up a chance at free food, Marui said yes.
Watermelon
Kintaro had gotten a watermelon flavored ponta, but turned out it was grape. Suddenly, Ryoma walked by, complaining of a vending machine out of his favorite drink, and Kintaro offered his, which Ryoma accepted before popping the lid off and saying thanks.
Xanadu
Sadaharu had finished working on his notes when he saw a xanadu colored bookmark Renji gave him. On the back, it read, "You have done good, Doctor. I hope we'll be an unstoppable team. - Professor."
Yellow
Ryoma was watching another fight between the dunk specialist and viper when a flash of yellow appeared that pounced on the two, knocking them down. It said, "Hey there, Koshimae!"
Zaffre
"Let's see, six letter word, a deep pigment of blue." Renji challenged his student on a crossword puzzle. Sadaharu laughed. "Zaffre." Renji chuckled. Oh, he taught his friend very well.