No argument intended, but believe me I've read a lot of stuff as well. But I've not read Runefang, and won't dispute that there may be information in that that is of help. You may be right about the color scheme in Beasts and Velvet, but I don't remember there being a color description.
And the tenuous tie between Sudenland and Solland is just that. In one line in the new army book it says that the old Sollanders call the area Sudenland because it's some sort of defiance. I think it's cool that they try to rectify the situation, because often times GW fluff doesn't even bother to mess with it. But in my mind's eye, they're two different entities.
There are similarities, it is true, the capital the same and the locations being relatively the same as well. So if people want to equate them as the same, that's fine, but I won't.
It's good to see, though, that Sollanders hold grudges more fiercely than Dwarfs. I think the part in Sigmar's Heirs about the lamentations of Wissenlanders for the fall of Solland is quite interesting. And something that most Sollanders would ignore.