Mohammad Mattar is one of at least 100 people who died during protests in Sudan last week.

He was 26 years old and had traveled to the capital, Khartoum, from London.

His death pushed people to turn their profile pictures on social media into different shades of blue, as a sign of solidarity with pro-democracy protesters in Sudan.

Blue is said to be his favorite color.

His friends started the trend as a way to deal with their grief.