I would avoid using red wine in a recipe that calls for white. Whites and Reds taste different, so you should expect a switch from white to red to be reflected in the finished dish. And, it will also change the color/presentation.

I was taught that white wine can be substituted with water and vinegar mixed in equal amounts, along with a small amount of sugar in recipes. I think they taste better with the vinegar/sugar combo than with actual white wine. Here's why: When you add alcohol to a recipe that is cooked, the heat evaporates the alcohol. In the case of white wine, the remaining flavor is tangy and tart. When you use vinegar/sugar in your recipe as a substitute for the wine, your recipe tastes like there is wine in it.

Now, we know that white wine isn't made from vinegar and sugar - so there isn't any alcohol in finished dish. It just has a flavor similar to the white wine. Whether you are out of white wine, or prefer to cook without alcohol, (and IMHO) the best substitution is vinegar and sugar.

Usually Not

It will depend on the recipe you are using, but often the flavor of red wine will clash with the fish (scallops, in this case). Most red wines have a higher iron content than most whites.

Here is an article citing the Journal of Agricultural and Food Chemistry which goes into more detail about this phenomenon.

I’m not sure exactly what dish you are planning to make but both chicken and scallops (like the big seared U-10s can go very well with certain red wines so I don’t see what the problem would be.

The overwhelming majority of people cannot really tell the difference between red and white wine in a blind taste test. This has been proven repeatedly in various tests - google it for examples. Even wine connoisseurs are fooled sometimes. Red wine will change the colour of the result but not the flavour (any more than the subtle differences in the taste of wines of the same colour).