FANTASTIC question and thank you for asking it because that does need clarification. You probably already know a lot of this but I'll just spell it out for anyone who doesn't.
The normal pH of your vaginal secretions are between 4 and 5 to kill off harmful organisms. However, for swaying purposes you want to know what the pH of your cervical mucus is, particularly your pH at ovulation. CM pH is typically quite a lot higher than vaginal pH but during your infertile days there is a thick plug of mucus blocking the entrance to your vagina so very little CM comes out during your infertile days. As ovulation nears, your cervix softens and this plug dissolves, and if you are very closely monitoring your cervix you can actually kind of notice this happening. Without the plug and with a larger opening in the cervix, the CM (which is now more alkaline and also much more plentiful) begins to flow out and it raises your pH into the 7's which is the healthy pH of both EWCM and semen, at which maximum numbers of both X and Y sperm survive. It is a matter of debate whether boy sperm really like super high pH and girl sperm like super low pH, or if higher pH sways instead by ensuring more sperm survive to make it to the egg and somehow higher numbers of sperm sway blue while fewer sperm (because less survive in lower pH) sway pink. Either way, the result would be the same.
For TTC pink you want less, thicker, and lower pH CM than you normally have and for TTC blue you want more, thinner, and higher pH.
For info and tips on how to check pH accurately read this:
How to check pH for DH and DW
For more info on CM and your cervix read this:
Tracking the three primary fertility signs (BBT, cervical position, and CM)