Here is the code I suggest:
% Creating map of Indonesian Archipelagos using etopo 1 sec
% Specifying the are to plot
latlim=[-12 10];
lonlim=[95 140];
worldmap(latlim,lonlim);
% Loading etopo data you can download from: http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO1/data/bedrock/cell_registered/binary/
[z,refvec] = etopo('D:\[MAPS]\etopo1_bed_c_f4\etopo1_bed_c_f4.flt',1,latlim,lonlim);
geoshow(z,refvec,'DisplayType','texturemap');
% Using demcmap color pallete and specifying the range for depth and hight
demcmap([-8000 400]);
% colorbar position and size
clb1=colorbar;
clb1.Location='South';
clb1.Position=[0.22 0.1 0.6 0.03];
clb1.TickDirection='out';
clb1.AxisLocation='out';
clb1.Label.String = 'Bathymetry, m Elevation, m';