Based on the data and code given below in the comments, you can build a custom colorbar with textboxes. The result is quite nice!
The below code shows the steps involved, however it cannot be executed without adding it to the code which is provided by OP in the comments.
p=cbp.Position;
w=p(3)/numel(sg)
cmap=colormap(jet(length(sg)))
str=sprintfc('\n Class %g',1:numel(sg))
for i=1:numel(sg)
annotation('textbox',[p(1)+w*(i-1) p(2) w*0.95 p(4)],'backgroundcolor',cmap(i,:),'string',str{i})
end
