We sometimes forget how important color and temperature are in assessing wines.
Years ago I participated in a blind-tasting competition in which all of the wines – a mix of reds and whites from Europe and California -- were all served at room temperature and poured into black glasses. That way, we couldn't use color as an indicator of age. We spit into black buckets as well.
After the tasting we realized how difficult it had been trying to decide which wines were which. The reds, for example, ended up being a comparison between aged Bordeaux and California Cabernet, and may have included a Louis Martini Zinfandel. The whites compared Chardonnay and Riesling. But we had a hard time knowing which wines were red or white since we couldn't rely on temperature.
It was fascinating to see how everyone struggled at identifying the wines! If you compare reds and whites of similar body, concentration, use of oak, etc., you might think that the biggest variable would be tannin in red wines. Yet barrel fermented, or oak aged whites can pick up tannin from wood and certainly have an oaky edge. Moreover, if you use mature wines, with say eight or 10 years of age, when the tannins in red wines have softened, it can be even more difficult discerning which is red and which is white. Wine’s inherent grapey personality provides the link between reds and whites.
Try the black wine glass blind tasting test some time. I'll bet you'll be surprised.