Blue
Shikamaru always knew that Natsu Sukai was different. As unique different. No it has nothing to do about the bijuu he already knew about that as he and Shino were told due to them being her best friends. She was different for her kind and soft personality. When she acted as Naruto he was loud mouth, played pranks, and only though about ramen, but when Naruto fell and became Natsu Sukai her real self she was softer, had an even softer voice than Hinata. Her eyes held no longer just blue but violet a perfect combination of both her parents.
Shino preferred the real her, Natsu Sukai. When as Naruto it was okay as it was for giggles and stupidity to hide from danger. As Natsu she played with him regardless of his bugs, and even fed his bugs her chakra. She never harmed a bug within his sight as she always caught and released them. Shino always thought her eyes were beautiful but dangerous due to the fact that Natsu Sukai held off her emotions when around fellow ninja showing nothing but a stoic face. When they weren't looking her eyes flashed with power underneath her tiny but dainty fingertips.
To them her eyes were not the color of blueberries. Her eyes were something more than just blueberries. Shino thought they were navy blue as when the ocean was covered by darkness. On the other hand shikamaru thought they were a type of blue-violet where you will only find them underneath the ocean looking for treasures or deep into HI no Kuni's mountains where there will be precious stones where you could not find anywhere nor make into jewelry from how rare they were.
When Kiba spoke to Naruto that day they were impressed with how stupid he could be as "his" eyes were more unique than that, but he choose blueberries.
"Yo Naruto you know your eyes look like blueberrie," Kiba spoke while having a team eat out with the entire rookie nine. With Naruto having an emotional control that could rival the ANBU gave Kiba a suspicious look.
" Well they're blue..." Naruto spoke without looking at Kiba more focused on his food.
"I know. I'm just saying you loud mouth idiot." Both Shikamaru and Shino looked at one another at the sheer stupidity of the dog ninja user. Naruto uncharacteristically sighed and gave a dead pan stare.
"Kiba. Shut up and eat." Kiba not getting the hint he turned to look at Shino and told him.
"Shino don't they look like blueberries?"
"..."
"Kiba you moron just shut up and eat you're going to need your strength for the next part of training. Troublesome."
"Fine." Kiba pouted while Akamaru gave a dog version of a snick. Behind everyone's back Naruto gave a thank you nod.