Can I reuse one tour's design on my other tours?

Yes. Save the tour's design under a name, then apply it to your other tours one at a time or many at once. Saving needs a paid plan (Pro, Agency or Enterprise); applying a saved design works on any plan. Only you see your designs.

Click Save & Render first, because a design copies what the tour has saved. Then, in the Advanced view, open Design tab > Themes (Design tab > Themes), go to the My designs tab, type a name under Design name and click Save design. On another tour, find the design under Saved designs and click Apply, or click Apply to tours… and tick up to 100 of your tours at a time. You can keep 50 designs.

A design holds the look: colors, fonts, bars, hotspot looks and icons. It never holds logos, pictures, panorama groups or labels you typed. Each tour keeps its earlier design in Undo history, and Restore brings it back. With Draft Workflows on, a tour shows the new design after Publish changes. My designs: save a tour's design and reuse it has every control.