Also i belive Svätoslava's eyes are most "original slavic". I always imagine ancient slavs as auburn haired with eyes like Svätoslava. What do you guys think which eye colour was predominant among ancient slavs?

I think that there wasn't anything like "original Slavic eyes" or "original Slavic hair". If we talk about original Slavs, about those without non-Slavic admixture, we have to go far and deep into the past. I don't dare to say what they looked like, however I can only give you my guess. Most of them had gray eyes and medium blonde hair. But honestly, I don't know..