I would try the saturation mod but by the time I've hacked a Vita for the first time I've already sold all my slims. I could just buy another slim.. but I highly doubt that the saturation mod solves anything. I mean, I guess it it depends whether the yellow is the result of software or hardware. I used to think it was like a R/G/B color balance setting on a monitor that Sony changed and arbitrarily made everything yellow, because they thought it was cool or something. But then later I heard it was done to save money (according to a former Sony employee) which would imply the screen is stuck looking that way, and at most you can try to mask it.
It would be extreme of me to buy a slim vita again, hack it, just to check out the color saturation mod for myself when I'm pretty sure it's going to suck. Then again, I'm pretty hung up on this issue and it's very like me to do extreme things when I become hung up on something. I've even considered taking my OLED apart solely to place padding underneath the dpad and start/select buttons to try and take away some of the edge the slim vita has over the OLED, and maybe even put a dab of WD-40 in the charging port to make up for the lack of micro usb, so at least it doesn't feel like I'm cramming a vga cable in a rusted socket every single time I decide to charge it.
For the record though you are able to use the same psn account to hack multiple Vitas right? Is there a limit? Though I hate how hard it is to deactivate a Vita the proper way. I keep getting the no response from server message. This might deter me from actually doing it, thank god.