Mark,
Not every shot works as well as the ones posted and I haven't got just one technique that works every time. I'm not qualified to give a tutorial on Photoshop but things I've had success with using Photoshop Elements 1.0 are:
1. Use the Enhance->Colour Cast. Initially I wouldn't use this tool as I thought it would be better to try and use less automated adjustments. However I've found there's nearly always something that should be white in pictures e.g. dead coral, stripes on fish. Click on these and you often get good results. You can always reset and try again if you don't like the result, also by clicking the preview checkbox on and off you can check the results against the original.
2. Create a New Adjustment Layer->Levels and adjust the levels of each colour in turn. I find it's best to leave the red to last and often find that you don't want to move the right hand slider right to the edge of the histogram as the the results often look unnatural.
3. Create a New Adjustment Layer->Hue/Saturation and reduce the saturation of the Cyan. This often removes the cyan cast you get on white objects. You can also try; using the sliders to change the range of colour desaturated; change the hue of cyans to be more blue; increase the saturation of reds and magentas.
4. Create a New Fill Layer->Solid Colour containing red/magenta. Set the layer mode to colour and play with the transparency until you get the colours you want.
You will often need to use more than one of these steps 1 & 2, 2 & 3 or 4 & 3. With practise I find that using 1 & 2 gives me the best results.
When you are ready to display your pictures or print them flatten the layers and use the Sharpen->Unsharp Mark tool to sharpen them up.
Good luck,
Richard