Yes, you can fully customize the ratio of how often a certain variation should be selected compared to your other variations.

Say you have three variations “Blue”, “Red” and “Green” plus the “Original” version. By default, Matomo (Piwik) allocates 25% of your traffic to each variation. You may also choose to allocate more traffic to “Blue” and “Red” while your “Green” and the “Original” version gets less traffic.