The change of fruit color associated with ripening of ‘Shine Muscat’ grape (V. labruscana Bailey × V. vinifera L.) is slight because the ripe berries remain greenish; therefore, color measurement requires high accuracy. We achieved this by image processing with a method of lightness correction using the image background and gamma correction. In the RGB color space, fruit color change followed a linear model. In the HSL color space, the hue value decreased and saturation increased continuously with fruit maturity. We developed a fruit color chart based on the fruit color change model. It presents color variations indicating maturation processes with 12 levels ranging from immature fruit to overripe fruit. We consider this method can be used in various grape production scenarios.

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