I believe yellow is better, but you don't exactly want "dark orange" either! (although I don't think it will hurt any, it will probably taste pretty strong)
Clear basically means more diluted from what I understand.
But that doesn't mean clear is useless. Minerals and nutrients may be more diluted, but there is more to UT than just that. One example: the urine is also "structured water", which even all by itself is a good thing, even if it had none of the other elements of urine in it. I'm sure there are also things like pH balance, "energetic" or "spiritual" concepts, homeopathic concepts, and other things along those lines to consider.
My morning urine is often more of a "golden" color. Not entirely yellow but not fully orange either... somewhere in between. This is especially true if I had stuff like red lentils and carrots the night before or vegetable soups, or dark green vegetables ... pretty much anything "rich" in color and nutrients. If my meal the night before was more light, and more fruit-based, then the morning urine tends to be more of the typical "mid-to-light yellow" color, depending on how concentrated it is.
Through the day as I drink more water, it tends to get more clear. Sometimes I'll recycle the same urine a couple times, and that makes it very clear, almost like water with just a HINT of very light yellow, and virtually tasteless (though the "smooth" texture is still nice!)
But basically, I don't think it really matters. If you make UT a "lifestyle" practice you'll take in a wide variety of fairly (or even heavily) concentrated (which might be hard to take due to strength), to diluted and almost tasteless and colorless. I think it all averages out...