Thanks for the effort but there must be a difference in the PS3 version, have you tried playing your method on the web version?
After level 1 I only have $134, in level 4 if you don't sell the red you can't purchase a blue during the level and I can't try most of the rest due to falling behind.
Send me a link to the one you guys are playing I will have a bash.
if you need to sell the red to buy the second blue go for it the reds kinda obsolete at this point
