Complex sentence: They were available in 4x2 and 4x4 models and offered only in black, red, orange or green; later in 1979 it was available in 6 colors.
Split into simpler sentences: They were available in 4x2 and 4x4 models. The 1978 models were offered only in black, red, orange or green; later in 1979 it was available in 6 colors.