In order to solve the uncertainty of voice-to-color conversion in which one of the three voice features(loudness, tone, rhythm) is applied to control LED color, a linear conversion solution is proposed. And a chromaticity diagram is defined by using hue definition on hue-saturation-lightness(HSL) hue ring and the normalization of CIE xyY which is a color standard defined by International Commission on Illumination(CIE). The chromaticity diagram shows a linear relation between pitch and color, which is referred to conversions of other physical parameters as well. Based on the solution, red(R), green(G) and blue(B) LEDs, the driving structure of a conversion circuit is designed and set up. The results indicate that signal processing of tone-to-color conversion is effective, from 30 Hz to 3 kHz with a resolution of 10 Hz mapped to the chromaticity diagram. In order to solve the uncertainty of voice-to-color conversion in which one of the three voice features (loudness, tone, rhythm) is applied to control LED color, a linear conversion solution is proposed. And a chromaticity diagram is defined by using hue definition on hue-saturation-lightness (HSL) hue ring and the normalization of CIE xyY which is a color standard defined by International Commission on Illumination (CIE). The chromaticity diagram shows a linear relation between pitch and color, which is referred to conversions of other physical parameters as well. Based on the solution, red (R), green (G) and blue (B) LEDs, the driving structure of a conversion circuit is designed and set up. -to-color conversion is effective from 30 Hz to 3 kHz with a resolution of 10 Hz mapped to the chromaticity diagram.