@_pinkypromise_x
For Gaara –
In Hurricane, Chapter 9 has Azmaria's image that I built her off of. She always carries a large sword on her, has dark hair [where the length has changed between long and pixie cut, but for the most part she always has longer hair] – 'jet-black hair and dark green eyes', and has gloves with no fingertips [a gift from Gaara].
Her first uniform was based off the yellow top and black knee length pants in the reference image. But after the time jump in 'I Fade Away', the 'Azmaria Fan Art' Chapter found after Chapter 5 is the best reference for her as an older teen and joining Suna's elite forces.
As for the 3rd book, she would have a different uniform having come from the Land of Lightning. And when she marches in with the Raikage and his army she's wearing – 'ninjas in long blue, thin material-like capes were marching in' – so open to interpretation, but her weapon remains the same.
Sanchi has auburn hair. Tamahome has black hair. Both are fifteen, three years older than Azmaria and Gaara at the start of the series. I guess I never gave them an eye color. But I always imaged Sanchi with light green eyes, and I have a reference image for him in 'We Are One', chapter 'Sanchi' between Chapter 4 + 5.
For Tamahome, maybe more of a dark blue to black in color, his reference image is at the end of the 'We Are One' book – 'Tamahome + Sakura' – after the Epilogue Chapter.
And I also have a reference image of the three of them together after Chapter 22 in 'We Are One', called 'Azmaria, Tamahome + Sanchi'.