%% 第一种
figure;
A = rand(3,4,3);
A1 = A(:,:,1);
A2 = A(:,:,2);
A3 = A(:,:,3);
contourf(A1,A2,A3,30); colormap('jet');colorbar;
my_handle=colorbar;
my_handle.Label.String = 'depth/km';
my_handle.Label.FontSize = 15;%% 第二种
figure;
A = rand(3,4,3);
A1 = A(:,:,1);
A2 = A(:,:,2);
A3 = A(:,:,3);
% my_handle.Label.String = 'Elevation (km)';
% my_handle.Label.FontSize = 15;
contourf(A1,A2,A3,30); colormap('jet');colorbar;
my_handle=colorbar;
my_handle.Title.String = 'depth/km';
my_handle.Title.FontSize = 12;%     t=get(my_handle,'YTickLabel');
%     t=strcat(t,'km');
%     set(my_handle,'YTickLabel',t);

第一种：

第二种：