Words referring to colors, like most adjectives in Italian, have different endings depending on whether they are masculine, feminine, etc.
Rosa (pink) and viola (purple) are different though. They never change.
The letter g in Italian usually sounds like g in get. However, when it comes before e or i, g sounds like English j.
If after gi there’s another vowel, g would still sound like j, but the i will be silent.
Did you know that in Italian the word blu usually refers to darker shades of blue? Use azzurro for talking about lighter tones of this color. It might sound weird, but for Italians these are almost two completely distinct colors!