sapphire73 - It's Summertime!
username: hawkeye978  title: Pacific Red Sky
Left is a top layer.
Left is a top layer for this example.
Luminosity Blend
In luminosity blending mode, the contrast comes from the upper layer.  The words black and white have the effect of removing color from the blend because there can be no color when luminosity is either completely dark or white.  The word red is roughly neutral in terms of brightness and so it picks up the underlying color and imparting a neutral brightness to the blend.
Color Blend
The words white and black are both neutral in terms of color.  So in color blending mode, they have the effect of neutralizing the background. The word red is, well, red, so it blends by making everything it covers red.
Color & Luminosity Blends
Right is a background layer for this example.
Lighten Mode
Keeps only the lighter pixels from the top layer.  Since the word black is at least as dark everywhere than the lower gradient layer, it doesn't make the blend.
Lighten & Darken Example

Right is a background layer for this example.
sapphire73 - It's Summertime!
sapphire73 - It's Summertime!
sapphire73 - It's Summertime!
See photo in original gallery.