Not currently as far as I'm aware, although it would be super useful (#justsaying ).
What I do in the interim is build tablet and phone formatted pre-themed apps using layout, colours, fonts etc. and encourage users to start with these as templates and build from there.
The templates also set up easy-to-reference colours and fonts, so for example you can "Set(myTemplateBGColour, Green)" up front and for new screens simply set the background colour to myTemplateBGColour. This works for pretty much any element, including headings, body text, icons etc. and is especially handy for brand-based colours that are RGB or hex specific.
We also built some of these to use centralised theming and an app that allows us to set up the theme by selecting colours, fonts, etc. and save them - changes are automatic without the need to publish an update and it can be managed centrally - it helps if you're prepared to fetch the data up front and it depends how far down this particular rabbit hole you really want to go as it can get quite complex! 🙂
In addition, you could also consider take a try to create a security group on your side, then add all members of your Org into this group. After that, share your app to this security group with Can Editpermission, then all members within this security group could run and edit your app.
More details about sharing an app within PowerApps, please check the following article: