Complex sentence: The source of this color is the "Plochere Color System", a color system formulated in 1948 that is widely used by interior designers, and in fact, teal was a heavily used color in the 1950s and 1960's.
Split into simpler sentences: The source of this color is the "Plochere Color System", a color system formulated in 1948 that is widely used by interior designers. Teal was subsequently a heavily used color in the 1950s and 1960's.