First was Skype, with a grass green logo, what later became sky blue. Skype is for Voice over IP or as easier to explain, a way phoning through Internet with or without PC. We see all around us headsets, phones, web cams and other accessories, branded or certified somehow Skype, telling us: Buy me and save money. Right. We started to use and see that works well. But we still spend a lot of money on mobile calls.
So what to do? Rebtel can be a solution, offering in 37 countries limited no. of free and next low cost international calls from mobile for a cost of a local call. System is quite complicated for free users, and seems to be easy to their paying customers. Still not a solution to reduce terrific mobile roaming rates, yet permits a nice saving for strangers calling their homeland, or who leads double life in two or more different countries with same no. of sim cards, etc.
Nice idea, explained well. Sure we are going to hear a lot about Rebtel in near future! So why title VoIP blue? Is it really revolutionary to use near same blue as Skype does? 
Just look at Rebtel logo and compare with Skype's:
