Proto-Indo-European Roots

Root/Stem: *bhel-
Meanings:  white, clear; to shine
Cognates: Greek phalios (white) - from *bhal-jo- (sometimes is believed to be borrowed from Pelasgian *balios, related to Thracian)
Latin flagrare (to shine); 
West Popular Latin blancus (white) - may be from Celtic; > 
Sardinian biancu, French blanc (white), baille (paleness), Occitan blanc, Spanish blanco, Catalan blanch, Italian bianco, Portuguese branco
Common Celtic *belo- (white, shining), > 
Gaulish Belenos (Apollo), Belisama - two gods' names from this stem; Old Irish beltene - May, May-day (from *belo-tine - white fire), Irish bealtaine, Scottish bealtuinn; Old Irish oíbell (flame); Welsh bal (white-faced)
Old Norse bál (fire); Gothic bala (paleness), Old Swedish blikan (to shine), Old English bli'can; Old High German bilisa (henbane); 
German erbleichen (to shine), English blaze, bleach, blond, bald, bale, black, Danish ba"ldet (naked, bare) 
Iranian (not found)
Sanskrit bhála- (a shine)
Armenian bal (paleness)
Thracian balios (white), 
Albanian balle" (a forehead)
Common Baltic *balo- (white, pale) > 
Lithuanian balas, baltas (white), Latvian bals (pale), balts (white), Sudovian bilsas (white), Old Prussian ballo (a forehead)
Common Slavic *be'lo- (white) > 
Ukrainian biliy, Bulgarian bial, Macedonian bel, Serbo-Croatian bio (masc.), bijela (fem.), Slovene bel, Sorbian bely, Slovak biely, Czech bi'ly', Polish bialy, Russian bely (white), bledny (pale)
Notes: The stem must have denoted a verb in Proto-Indo-European meaning "to be white", but soon it turned into an adjective in many languages. Derivatives are a long list, and additional meanings were "flame", "fire", "pale", "bright", and even some strage ones such as English black. The influence of Celtic languages on Popular Latin generated Romance blancus and its descendants.