:: tutorial .005
Start with your base, sharpen once and desaturate if the image isn't already black and white.
Duplicate once and set to overlay 100%.
Take this and set to screen at 100%. Move it to somewhere that looks good on your icon.
=
Using a dark blue color, (I used #00022A), set to exclusion 100%.
=
Use a light blue color, (#BAF1FF for me), set to color burn at 100%.
=