There is no single function that can do this. You will need to use a collection of find_system and hilite_system to do this. Example below.
% Get highlighted blocks. Idea is to look for all blocks with yellow background (default highlight color).
% This results in a cell array of paths to all blocks that satisfy this condition.
% Note that if your highlight color is different or more than one color, you would need to run an
% appropriate or multiple commands to get the list of all blocks highlighted no matter what color.
hilited_blocks = find_system('my_model','BackgroundColor','yellow')
% Pass block list to hilite_system to switch 'off' color.
hilite_system(hilited_blocks,'off')
