I've been trying to change the layer's pixel width and coloration using ArcGIS Online, but the changes I make to the layer don't seem to save. Any help would be wonderful.
Are you saving the map as a whole or saving the layer? If you are not familiar with where to do this on the map viewer, click on the ellipsis next to your layer to open up the options and you should see options to save and save as. Choose which one is most appropriate for you and that should save any changes to symbology.