Thought I had answered, but apparently it got lost.
I'm sighing, because again (probably due to trainings/books that omit coaching good practice) you have a problem because you didn't set up styles properly before creating the project but want to do this later? Same problem I have seen in my teaching career for word processing, desktop publishing, technical drawing... In Dutch we say 'Reflect before starting much easier than remediating later'.
Each object in the Object Style Manager has 3 styles, one for each breakpoint view (and the shapes, even though they are not defined in the OSM as buttons have 3 states as well). That is the biggest change since many versions in the OSM and no one talks about it AFAIK (I start with that when showing new features). Styles for possible text containers (captions, shapes) do include the font, font color, font size. You can clone styles as you probably know. If you change the default styles in the OSM, and then create the project, there is no problem. Now you can change the default styles in the OSM and they will be applied automatically to all objects that use those default styles. I just hope that you didn't override the Default style, another bad practice that I'm seeing regularly when debugging projects. Sorry for my ranting, but the tons of hours that get lost by bad practice cannot even be estimated.