St Peter was Jewish - in ethnic terms Semitic - which is a subset of the Caucasian race.
There were several early Popes who were North African, however this too is considered a subset of the Caucasian race.
So it depends on exactly what your friend means by ‘white’. Certainly St Peter and the others were not European if that is what she means. But they were Caucasian rather than (and this is meant with absolutely no offence) Negro. However, you might point out that St Peter and the other were every bit as ‘coloured’ as any Negro - just a different colour
More important - why should it matter to anyone?
God has called plenty of fine Negro men and women to be saints - examples that immediately come to mind being the Ethiopian converted by St Philip in scripture, St Moses the Ethiopian and St Josephine Bakhita.
Further, the Holy Spirit has conferred eligibility for the office of Pope upon a number of outstanding African cardinals, particularly Cardinals Arinze and Turkson who have both been remarkable servants of the Church. This being the case, He surely would not let something as unimportant as colour dissuade Him from effectively guiding one of these men should they be elected.