I thought I could share my SilverBlue/SilverRed themes. I use them since 4.1.
Porting it to 4.2.0 took some time since the docs/guides regarding theme creation/sencha cmd are currently not really up to date. That's why I think sharing the source could be helpful for you.
How to do a theme is mentioned in short by @london_lawyer in this post.
The theme is self created (not a copy of the steelblue theme, although nice to see that somebody had a similar idea ).
All icons that are not only white/blue/red (the colorful ones) are from the fugue package.
The others are images from extjs classic theme or self created.
Use the themes as you want. Feel free to modify and help to improve them.
Programming today is a race between software engineers striving to build bigger and better іdiot-proof programs, and the universe striving to produce bigger and better idiots. So far, the universe is winning. (Rick Cook)