Correct me if I'm wrong, but it seems to me like blue is faltering. Sure, he'll take the flat rate on his turn, and he may fight back against pink, but he's against both pink and yellow and have little chance of coming back. Also, it seems like you only control the Middle East while Blue is the only thing that is threatening you, green, yellow, and pink. Which means that once blue is out, green and yellow will have N.America and Australia back respectively. The only time to attack is now. End the truce with Pink, and take his territories. When pink is out, Blue will still be up against yellow and green and probably won't attack you due to your alliance. When the game is down to four, you should aim to take out Green ASAP. Hopefully, you'll be able to eliminate him and get his cards, which would allow you to collect another bonus and continue your expansion. By this time, the strongest player would be blue (with S.America, Mexico, parts of Africa, and parts of Australia) , with you second (Middle East, Parts of Australia, Most of Asia and most of Europe) and yellow third (Parts of Europe and N. America).
If possible, ally with yellow and give blue a one turn warning (although when there are only three players left, it's almost understood that old alliances are off). Give yellow Europe so that you can take full control of Asia and combine forces to destroy blue. When you do so, you should have Australia, Asia, Africa, Middle East, parts of Europe, leaving yellow with parts of Europe and N.America, and parts of S.America. If all goes well, you'll take out yellow with little resistance. (if everything goes as I said

)
Best case scenario would be for blue to attack you without warning. Then, no one cares about etiquette and you'll be able to ally with yellow, and reduce blue's power without having to warn blue first.