Yet another way for all interested:
As of Photoshop CS5, there are 2 new blend modes: Subtract and Divide. So there is a way to solve this task using just these modes.
1. Find the channel with the most contrast, in your case it's Blue channel with 57 value for background and 255 - for white text.
2. Create new layer.
3. Use Appy image with the Source layer Merged and Blue channel and Normal mode to fill this layer with the Blue channel.
Now we are going to apply the formula (x - 57)/(255 - 57) to this layer, where x is the Blue channel value.
4. Create new layer, fill it with 57 Gray.
5. Go to our Blue channel layer and use Appy image with the Source layer from step 4 and Subtract mode.
6. Create new layer, fill it with 255 - 57 = 198 Gray.
7. Go to our Blue channel layer and use Appy image with the Source layer from step 6 and Divide mode.
Here we are: our Blue channel layer now can be used as the mask to separate the text from the background. Load it as a selection(Ctrl-Alt-2) and create Solid color fill layer. Drop some background layer behind it.
