I tested this and I don't see the problem getting fixed changing the value.
The problem is that the Engine calculates
Prismatic Omen as something that could change or give 1
X 
and not more so only if you have an untapped Blue source of mana and non-blue untapped producing Lands will
Counterspell work.
It also works fine if you have in play 2
Prismatic Omen and no blue mana producing lands as it calculates each
Prismatic Omen for a

source so
Counterspell plays fine.
Edit Also having to do with above bug(a less important bug)is that with 2 and more
Prismatic Omen on the battlefield and only 1 Land the engine believes there are as much mana available as the
Prismatic Omen on the battlefield are.