We don't know why it is red. - Amy Simon-Miller

Red Spot Jr  made its closest approach to the Great Red Spot on about 15 July when the edges of the storms were about 3500 kilometres apart. They will probably completely pass one another by the end of July. 

Red Spot Junior has made its closest approach to the Great Red Spot on Jupiter, but the pass has not visibly diminished the strength of the smaller storm. Nonetheless, astronomers are maintaining their close watching on the two storms.