Colour Ramp Editing the Easy WayBefore you start you'll need image editing software and a copy of s3pe. I used paint.net for editing the colour ramps and highly recommend it - it can open and save in the formats required for this process without any need for secondary conversion/extraction measures.
Incredibly helpful links:
Massive thread full of colour ramp and general world customisation infoThis post provides an overview of which files contain which colour rampsLabelled colour rampEditing the ColourOpen up your image editing software (in this case, paint.net). Use it to open the .dds file with the colour ramp you wish to edit.
Use the area selection tool to highlight the specific colour ramp you wish to edit (in this case, we're altering the water).
Once it's been selected it's easy to play with the colour using the Curves and Hue/Saturation options in the Adjustments menu.
Selecting RGB mode in the curves menu lets you adjust the red, green, and blue values of the colour separately or together. Check or uncheck the value you wish to adjust, then click on the grid until the curve(s) create the colour you want.
The colour can also be adjusted through the Hue menu sliders. It can make the colour lighter or darker, and more or less intense.
There's probably other options (and most likely better ones) for adjusting the colour, but these two are very simple to use and great to start out with. If you know of something even simpler and easier please feel free to share it - I'm a paint.net novice!
Once you're happy with your water colour it's time to save. Make sure the ramp is saved as A8R8G8B8 and that Generate Mip Maps is NOT checked.
Putting the Altered Colour Ramp Into Your WorldNow that the ramp is done and saved it can be imported into your world. To do this fire up s3pe and open up the .world file.
Under the Resource menu select the Import -> From File option. Select your altered .dds file(s). This is also how you can add any altered .ini files to your world.
Save the .world file. That's it! When you next open the world in CAW the altered water colour will appear.
It's very easy to make and check the colour ramp changes this way. With paint.net, s3pe, and CAW open a ramp can be opened, changed, saved, imported, saved, and loaded very quickly.
Just remember that altered colour ramps DO NOT save in CAW. If you want them in the final version of your world they'll need to be added to the .world file before it's exported for the last time.
That's it! Have fun, play around with the colours, and let me know if you have any questions or helpful tips.