My experience working with children and using other types of crayons, construction paper or paint, know that kids are uninhibited by any social convention about their choice of skin color.
First and second graders used these markers for their particular self-portrait lesson at the start of this school year.
I set the markers out organized on the front table with sample cards. Students used the cards to match their skin color and chose their marker to complete their drawing.
They did a great job and hopefully they reflect the variety of students we have at our school.