Race: The term "Arab" does not refer to a particular race. Arabs include Caucasians and Africans with ancestral origins in Europe, North Africa, and the Middle East. The intermarriage of Arab seamen and their agents as far back as the first century [13] has left few 'pure' Arabs, racially. "Dark skinned" Arabs are Sudanese, Ethiopian and Somalian Arabs, and Arabs from Southern Egypt who are considered Africans. "Caucasian" Arabs are Arabs native to Syria, Lebanon, Palestine, Tunisia, Algeria, and Libya among others.
http://www.newworldencyclopedia.org/entry/Arab
Arabs are Semites. Semites are Caucasians
https://en.m.wikipedia.org/wiki/Caucasian_race
There are two other races besides Caucasian. Negroid and Mongoloid. Some Arabs may be Negroid - Somalis.
" The Caucasian race (also Caucasoid[1] or Europid[2]) is a grouping of human beings historically regarded as a biological taxon, including some or all of the populations of Europe, North Africa, the Horn of Africa, Western Asia, Central Asia and South Asia.[3]
[3]"This third racial zone stretches from Spain across the Straits of Gibraltar to Morocco, and thence along the southern Mediterranean shores into Arabia, East Africa, Mesopotamia, and the Persian highlands; and across Afghanistan into India[...] The Mediterranean racial zone stretches unbroken from Spain across the Straits of Gibraltar to Morocco, and thence eastward to India[...] A branch of it extends far southward on both sides of the Red Sea into southern Arabia, the Ethiopian highlands, and the Horn of Africa.
https://en.m.wikipedia.org/wiki/Caucasian_race