[Niksko]

Because there is a fundamental difference in how they're made: red wines spend more time in contact with grape skins, while white wines don't. Grape skins contain tannins and other compounds that end up in the wine, and humans can perceive these compounds. You might question whether there is enough difference to warrant the perceived difference in flavor, but there are definitely quantitatively measurable differences in composition of typical red and white wines that would lead you to posit that they would taste different.

[darkerside]

I'm not saying they're literally the same. There are also invisible differences between any two wines that have MUCH MORE impact on the taste profile. Red and white can even be the same grape. Are the skins really more impactful than, for example, the type of grape, how the wine was aged, or for how long?

Why is the color so important? Mostly because it's visible to us noobs.