The Kohaku is the most popular variety of Nishikigoi. So much so that there is an expression, "Koi avocation begins and ends with Kohaku."
There are various tones of "red" color - red with thick crimson, light red, highly homogeneous red, blurred red, and so on.
There are all sorts of "Kiwa (the edge of the
pattern)" -scale-wide Kiwa, razor-sharp Kiwa, and Kiwa resembling the edge of a torn blanket, etc.
Shades of white ground (skin) are quite diversified too -- skin with soft shade of
fresh-unshelled, hardboiled egg, skin with hard shade of porcelain, yellowish skin, and so forth.