Programmatically changing underline color of EditText

@degs's answer is correct. But just add one little note: the AppCompatEditText#setSupportBackgroundTintList is now annotated with @RestrictTo(LIBRARY_GROUP) which means:

Restrict usage to code within the same group of libraries

Instead use ViewCompat#setBackgroundTintList. So in your example, it should look like this:

ColorStateList colorStateList = ColorStateList.valueOf(color);
ViewCompat.setBackgroundTintList(editText, colorStateList);

You need to set the backgroundTintList (or supportBackgroundTintList) on the EditText to an instance of ColorStateList containing only the color you wish to change the tint to. An easy way to do this in a backwards-compatible way looks like this:

ColorStateList colorStateList = ColorStateList.valueOf(color);
editText.setSupportBackgroundTintList(colorStateList);

This will give the EditText the desired underline color.