What does yellow indicate racially in the UK?
Of course in the UK Asian mainly means South Asian while in the US South Asian people usually are not even included in Asian and are seen as another category.
In the US yellow skin color does refer to Asians and Asian people there don't much like it, but I don't think it's a severe slur either.
Also in the US there is "high yellow" which is a derogatory reference between black people referring to lighter skinned black people who may be putting on superior airs.
Of course I don't see the point of censoring the song unless there is UK thing that I don't know about.
I don't think the race of Mathis makes any difference in this.