Transparency of rectangle disappears when saving as fig?

I can't figure this one out from past posts:

I add a transparent rectangle (alpha=0.3) to my plot:

rectangle('Position',[135 0 30 0.2], 'FaceColor', [0.2000 0.8000 0 0.3])

Then I want to save as a .fig file for later data processing:

set(gcf,'units','normalized','outerposition',[0 0 1 1]) 
savefig([root_dir,subnum,'/03_TMS/04_EMG_SPs/03_Plots_Tables/Individual_Graphs/',trialName,'_stim',num2str(j),'.fig']);

However, savefig gets rid of my transparency. The examples I could find discussed how to deal with this when you want to keep a transparent background / save as a .png image. How can I save as a .fig file and keep my transparency?

[Jan]

Currently you showed only, how you save the file. A file does not contain transparent objects, but they appear transparently, when you open the file and create a new figure. So please add the code you use to open the figure. Does it set the renderer to painters implicitly? You need OpenGL for transparency.

[Kathleen Hupfeld]

Ah ok all good things to know, thank you for your input!! I was just using GUI to open the .fig files (i.e., file->open).

I ended up working around the problem by just making a lighter green rectangle first, then plotting the EMG signal I'm working with over top of that rectangle, so it doesn't matter that it won't reopen as transparent.