Fresco creates its files with sRGB profile embedded. You can verify this yourself:
1. In Photoshop, go to Edit > Color Settings, and set your working space to ProPhoto RGB.
2. In the same dialog box, set the color management policy to preserve embedded profiles, and to ask when opening for missing profile:

3. Open a Fresco document, then choose Edit > Convert to Profile:

Here you can see that the file (in my case, a drawing created in Fresco) has a profile of sRGB even though my Photoshop settings have a working space of ProPhotoRGB.