I, too, have a hard time matching colours on the comparison tubes. I think colour perception wanes with age somewhat.
While I cannot tell the difference on the TC bar for values 3 or 5 I
can see that it's not 1. 2 is up for grabs most days. Since I do the titration twice a week it's good enough for me knowing that on the in-between days the TC is at least equal to or greater than 2.
pH is similar. I know that it's
not 6.8, 7.2, 7.8, or 8.2. Therefore, it's between 7.3 and 7.7. Again, good enough.
Last season I stressed over not being able to do a better job reading those colour bars and yet the pool was clear and clean all season. IT doesn't know that my eyes don't work as well as they used to
AnnaK