Whats the correct ph?

Ive only got one of those cheap ph testers where it changers colour, are they any good? on my last grow i made it greenish yellow colour which i believe is between 6&7 any help is appriciated thanks.

For soil, if you can get that bright orange / yellow at 6.5 that is perfect. For hydro look for 5.5 - 5.8

thanks alot mate much appriciated

6.8 to 7.0 for soil.