It seems like it's not defined in the convention (International Convention on the Elimination of all forms of Racial Discrimination). But does race only mean colour in the convention?
Article 1 of International Convention on the Elimination of All Forms of Racial Discrimination (ICERD) defines "racial discrimination" to mean "any distinction, exclusion, restriction or preference based on race, colour, descent, or national or ethnic origin which has the purpose or effect of nullifying or impairing the recognition, enjoyment or exercise, on an equal footing, of human rights and fundamental freedoms in the political, economic, social, cultural or any other field of public life."
The Committee on the Elimination of Racial Discrimination CERD is the observing body for the ICERD and has not seen it necessary to define "race" under this instrument. To the contrary, it has adopted General Recommendations that clarify that the protections apply to particular groups of people without stating which of the listed categories they are best captured by. See this Introductory Note:
CERD has adopted General Recommendations to clarify that the ICERD protections in article 1 include groups not explicitly named but who fall within the Convention’s broad criteria, such as women (G.R. 25), indigenous persons (G.R. 23), the Roma (G.R. 27), Dalits (G.R. 29), non-citizens including refugees (G.R. 30), African descendants, particularly those in the diaspora (G.R. 34), Muslims subjected to Islamophobia, and more generally persons whose religious identity has been “racialized,” that is used as a basis for discrimination (G.R. 32).
In fact, the use of the term "race" was and is a contested aspect of the convention, as revealed through the travaux préparatoires (Patrick Thornberry, The International Convention on the Elimination of All Forms of Racial Discrimination: A Commentary, Oxford University Press, 2016). The UNESCO report, "The Race Concept: Results of an Inquiry," was available to the drafters of the ICERD and it asserted that "[t]here is no evidence for the existence of so-called 'pure' races." Some (e.g. Vieno Voitto Saario) were of the view that "race," "colour," and "ethnic origin" "all meant much the same thing." It continues to be argued that CERD should "repudiate the notion of race."
does race only mean colour in the convention ?
Not exactly, because colour is listed on its own:
- In this Convention, the term "racial discrimination" shall mean any distinction, exclusion, restriction or preference based on race, colour, descent, or national or ethnic origin...
A precise, explicitly defined meaning of "race" (as opposed to the ordinary meaning widely understood back in 1966 — even if fuzzy) lacks significance in the context of the convention because the term is used to refer to what possibly can be discriminated upon — and any such discrimination is condemned.
If the purpose of the convention was the opposite — to promote racial discrimination — then the precise meaning would need to be defined because otherwise it would be unclear when exactly to discriminate. But, thankfully, the convention says: don't. Whatever meaning of "race" you can think of — just don't.