There are settings, that allocated for each spline. These settings can be saved/loaded to/from disk. They include different colors, different settings for each field (like position, controls etc.), spline showing options etc. There are a lot of things you can customize. These settings are located under Fields and Settings tabs.
How to change and Save/Load Personal Settings
Settings are stored under 2 tabs- Fields (for positions and controls ) and Settings (spline related). After you make all the changes you can save settings either as default or some custom profile. Choose Settings tab and open 'Save/Load' foldout.
Shared Settings for all spline
There are also settings, that are shared by all splines. These include color of rectangular selection, on/off mode for menus etc.These settings are accessed by pressing Gear icon.