1.Install skin mod first.
2.Download Ego ERP Archiver 7.1 or newer here:
Ego ERP Archiver by Petar
If you do not want to pay, then click little line "No thanks, just take me to the downloads"
3.Open folder Steam\steamapps\common\F1 2020\2020_asset_groups\f1_2020_vehicle_package\teams and find erp file of each team.
For example Ferrari: Steam\steamapps\common\F1 2020\2020_asset_groups\f1_2020_vehicle_package\teams\ferrari\wep\ferrari.erp
4.Open erp file in Ego ERP Archiver, in tab Xml files - click .vtf file (for example ferrari.vtf), click xml files -> import, and choose xml file from mod. Mercedes.vtf located into Common.erp, not in Mercedes.erp.
5.Save and repeat for each team.
6.Enjoy. Good luck !