Stan, the color of wood glue on the surface should be totally irrelevant, because the last thing you want with any stock repair is glue on the surface. It will stain the wood and act like a wood sealer, and interfere with staining and final finish.

Maybe it's just me, but I'd rather not have to resort to some dark built-up finish to attempt to conceal a glue joint. Although I have also found that the choice of final finish does have an effect on the visibility of a repaired area. In other words, some finishes may make a repair joint stand out, while others make it far less visible.

I really like Titebond II for repairs in walnut, simply because it gives me the most invisible joint of anything I have tried. Even in rather dark Black Walnut, a Titebond II glue joint is not lighter than the wood on either side of the crack. With a good close fitting joint and correct clamping, the glue joint is often almost invisible, which is exactly what I want. Good epoxy and Titebond III are slightly stronger, but a sound split wood repair with Titebond II will in most cases be stronger than the surrounding wood, and that's good enough for me. Of course, that statement on strength of the joint will not apply to an end grain to end grain joint.

There are other times when Titebond II is not the best choice, such as when gluing stock wood that may have some oil contamination. In that event, I would likely choose a polyurethane glue. But I find that polyurethane glue is messy to use, and any foaming or squeeze out that is on the surface takes more sanding to remove so that it won't act like a sealer. The shelf life of polyurethane glue is pretty short too. I would be much more inclined to choose a good epoxy when the glue joint is not on the surface, such as when repairing a split or crack in the inletting, or when embedding some reinforcing pins, dowels, or tenons. Epoxy is always better for gap filling too, but of course, such repairs will be easy to detect. And if I have to mix some fine sawdust with epoxy to fill a gap, inclusion, or defect, I find that pine sawdust is often a better choice than walnut sawdust, because the walnut sawdust and epoxy mixture will typically be much darker than the surrounding walnut. Pine sawdust mixed with epoxy will often give a much closer color match on a walnut repair.