You can create a profile in Full mission builder and also in the options/plane area, if you click on loadout.
There you can setup the ammo on the belts, on each individual gun, however you want. You do this by moving the type of ammo you want in the belt, in the left window.
Let's say, in hurricane you have five rounds in the left window, out of wich one is tracer (white).
What ever the sequence is loaded in the left window, that sequence is going to repeat in the entire belt. You want more tracers, just drop one more tracer from the right window into your belt (left window). You want only tracers, you remove everything except the tracer.
You can do that for every gun, and you don't have to load all guns the same.
When you are done, make sure you save the loadout with "save as", and give it a name. That name will show up in your missions screen, in the drop down menu, just under the image of the plane you selected..
Here's one example i did just for fun, to look good on screenshots.
Simply i loaded in four guns just one "Navy tracer" (because is red)
, one AP and one Incendiary. In the other four guns i loaded only AP and incendiary.
Here's the result:
