Ne-IRO is a compound word of Ne and Iro. Iro means color and Ne can be alternatively translated as tone, sound, voice or timbre. So Ne-Iro can be translated ``tone color'', but it implies much more nuances concerning music and sound perception. We can find the example of NE in the first paragraph of Makura no Soshi-枕草子, which is a Japanese classical literature written in the 8th century; Mushi no Ne, Kaze no Oto (sounds of the insects, sounds of wind in autumn.) In the Western culture sounds of the insects have been noisy, but Sei-Shonagon 清少納言 loved it. This is an example which shows that NE 音 includes special emotion of the person who uses the word.
The Kanji for OTO is same as that for NE 音. Since Heian era(794-1192), the same Chinese letter 音 had two Kun-yomi 訓読み (a Japanese reading of Chinese letters, using the Japanese original pronunciation which has the corresponding meaning); NE and OTO. It is certain that ONSYOKU is also a compound word OTO(sound) and SYOKU (color), and NE-IRO and ONSYOKU have the same Kanjis 音色, but the two are different in the point that ONSYOKU is the modern translation from the Western word `timbre', while NE-IRO is the traditional word. HIBIKI also means integrated sound in musical and social space.