I've colored jenga pieces to play uno stacko. House rules for extra blocks?

The other day, a friend said they really liked playing uno stacko at someone else’s place. I just half assedly painted mine, but yellow marker was barely visible for the numbers, so I had to use another color

However, uno stacko has 45 pieces and I ended up with an extra blank piece for each color, and two completely blank ones, as seen on the top. Which house rules would you suggest for these extra blocks?