ðɛɹwˌɜː mˈɛni ˈɜːlɪɚ jˈuːsᵻz ʌv kˈʌlɚ tə vˈɪʒuːəlˌaɪz kˈɑːmplɛks fˈʌŋkʃənz, tˈɪpɪkli mˈæpɪŋ ˈɑːɹɡjuːmənt fˈeɪz tə hjˈuː.
There were many earlier uses of color to visualize complex functions, typically mapping argument (phase) to hue.