In RCT2, you can change the water colour when you make a scenario. What you actually do when you change the water colour is that you load a new selection of colours that the game will use for that map. A person by the name of ja227 created an application that will allow you to change the palette of a map with colours of your choice. This has been used in some maps to change the colours of peeps, for example. The colours of the user interface are also taken from the palette.
Some parks with a different palette:
https://www.nedesigns.com/park/3410/h2h7-finals-asteroid-fields/ - Peeps are turned green
https://www.nedesigns.com/park/4092/h2h8-r2-mictlan-la-tierra-de-los-muertos/ - Peeps are turned a ghostly white
https://www.nedesigns.com/park/4087/h2h8-r1-all-coasters-go-to-heaven/ - Every colour has been made a bit more bright
How to make a palette
First off, here is the zipped application (by ja227):
Now, when you have unzipped the folder somewhere, you find the following contents:
When you open one of the BMP files, you will see an RCT2 palette:
Each pixel represents a colour the game will use. If you colour something on the map red for example, the game will use the pixels around the red colour to colour the item depending on the viewing angle. Some of the colours are used to colour peeps. If you change those the peeps will get a different colour. If you change the brightness of this image, you can make all colours in the map look brighter. The easiest way to edit the palette is by taking some photo editor software, select the part you want to change and then change the hue, contrast or brightness to your liking.
Now as an example, I will make a palette that inverts the colours of the map. This may not be very useful in a map, but i think it gives a good example of what is possible with palettes.
Now, first make a copy of WTRCYAN.bmp, and edit it to your liking. I selected the entire palette and inverted the colours in microsoft paint:
I called the resulting image WTRINV.bmp. Make sure you save it as a 24-bit BMP! Also, make sure the name you give it is not used by any other objects in your object folder.
Now, you will see a .bat file named RCTPALMAKER.bat. Make a copy of this and call it RCTPALMAKER2.bat. Edit this file in notepad. In the batch file, purple water is used as an example. You should change the names to fit your palette. Here's how I changed mine:
When you are done editing the batch file, save it and close notepad. Now you can run the file by double-clicking it (if windows allows you to run batch files).
If successful, you should see the following in your screen:
You should now have a file called WTRINV.DAT in your folder:
This object should then be moved to your objects folder. For OpenRCT2 this is usually Documents/OpenRCT2/Object
Now when you make a scenario and you go to Object selection, the palette should be available to you in the water color selection:
Now, this inverted palette is probably not very useful, but it sure gives a dramatic effect
Anyway, good luck and have fun creating new palettes!
Thanks to Liampie for providing me with the program! Credits to ja227 for creating it!