While paste tomatoes tend to have a higher pH, others are similar in acid (pH) ranging generally between 4.2 and 4.8. There is not a meaningful correlation between tomato color and pH, so no reason the think black or pink tomatoes will have a higher pH. The pH varies more with ripeness, soil and growing conditions than color or variety.
For canning, the rule of thumb is that a pH above 4.6 requires adding acid and/or pressure canning to avoid botulism. Most tomatoes are below 4.6 but about 15% of samples test above. Other factors affect pH as well in canning, such as degree of ripeness and added vegetables. Therefore most experts recommend adding acid to all canned tomato products whether canned in a BWB or pressure canner. This can be done with vinegar, lemon juice, or citric acid, the latter having the lease effect on taste.
Here is some good reading on the subject:
http://www.uwex.edu/ces/cty/pepin/fl...rtandTasty.pdf
TomNJ