I can not direct you to a signature site, but I can address the value differentiation between gold and Blue. My experience is, regardless of house, that the blue generally commands a higher price than the gold. Depending on company and rarity of shape the price bump generally appears to be around 20% or more for blue over gold.
In the case of some of the Steuben Aurene pieces in rare colors, they are in a completely different range regardless of shape..... a red Aurene hearts and vines Steuben vase has brought as much as $30,000, while a nice example of the same shape in gold or blue would generally be under $2000
Craig
Edit: The shape appears to be right based on some examples of threaded pieces I found. Most signed examples I found (not a whole lot) showed the company name, and also a numeric id such as 1812-7 which I found on the underside of a threaded piece in the same shape as the pictured vase in a Durand decor which won an award at the Sesqui-centennial International Exposition held in Philadelphia in 1926. (150th anniversary of the signing of the Declaration of Independence). I also found information indicating that the "u" in Durand may be in the form of a "v" in later signatures. Earlier examples were apparently not signed but later pieces were.