"Sips" can come in a variety of colors, as there are different morphs. "Blue sips" might be what most people think of them as looking like, but their are bright yellow/green forms (green leopards are what they are also called by patrick). This is what is looks like you have.
"Nikitas" which you referenced, look exactly like citronellas... only half their size, if that. Quality exotics (http://www.qualityexotics.com/frogs.htm
) has a good picture of nikitas on their site (two pics above citronellas to compare), as well as the green sips (which are just above pics of blue sips for a nice comparision). More pics of this morph can be seen on http://www.saurian.net
under the lable D. tinc "green leopard", which is the same thing.