Caucasian is a bullshit made-up pseudoscientific word that has little to nothing to do with anything.
While 'Hispanic' is slightly better as it is generally used in the US as a term for the peoples that arose out of the Spanish conquests and not so much for the "Of Spain" it originated as. It isn't of much use if you want to be exact, though if you aren't being an ass it is pretty easy to know what is intended with it.
Jessica Alba does not look Germanic, Nordic, Arabic, Slavic or Anglo, nor particularly Mediterranean. While she clearly has mostly European features, the features she did inherit from her Hispanic/Mestizo father mark her as clearly something other than pure European, or Caucasian if you must, just as someone who is one fourth Japanese or Indian or Ethiopian or Inuit would. Skin tone or eye color is such a minor factor in making someone look one ethnicity or another that it is hardly worth bringing up unless it is notable for its rareness globally such as an entire population with light blonde hair and fair eyes. A Swede will probably still look like a Swede to anyone familiar with Swedes even if you dye his hair and give him contacts, just as certainly as Jessica Alba couldn't be made to look as 'white' as Chris Evans no matter how much they clearly tried.
In closing, they should have just let her look like herself and explained it away as having different dads or moms or cast a brother who was less white-bread. That whole mess and this whole argument was born out of a desire to please fanboys while never actually thinking through what the problem was in the first place.