To improve DOSBox performance make the following changes to the DOSBox configuration file:
The latest official patch is version 1.31, which can be found here. There is also an unofficial 1.50.8 patch here (includes a windows-based launcher and optional mods). An older fan patch, 1.40, can be found here in-case 1.50 has something you don't like. Also note that the digital versions have 1.40 pre-installed, info for reverting which back to 1.31 can be found here. Additional patches/mods (possibly obsolete) can be found here, here, here and here.
A reversed engineered source port is available.
See Rainbow color problems in older games.