How many Pact Shards can I obtain without moving to the next threat level?
It seems there is no way in game to tell until you have reached the next floor,
however over the past week I've been collecting data, and although I don't have everything yet, I do have what I feel is enough for an answer. I fully intend on adding to this answer in the future.
My data so far: (all from Cov25 runs)
The blue colour represents numbers that are not yet final, for example I do not yet know what the lowest Yellow on Level 6 is at the moment, but it will be either 35 or 40.
So what I do know is:
On Level 1:
if you pick up either the +10 (for gold) or +15 (for an artifact), you will go into Yellow,
otherwise the first fight is no threat.
On Level 2:
15 Pact Shards you go into Yellow,
30 Pact Shards you go into Orange,
40 Pact Shards you go into Red.
On Level 3:
20 Pact Shards you go into Yellow,
35 Pact Shards you go into Orange,
50 Pact Shards you go into Red.
On Level 4:
25 Pact Shards you go into Yellow,
45 Pact Shards you go into Orange,
65 Pact Shards you go into Red.
On Level 5:
30 Pact Shards you go into Yellow,
55 Pact Shards you go into Orange,
80 Pact Shards you go into Red.
On Level 6:
between 35-40 Pact Shards you go into Yellow,
65 Pact Shards you go into Orange,
100 Pact Shards you go into Red.
On Level 7:
45 Pact Shards you go into Yellow,
85 Pact Shards you go into Orange,
between 120-125 Pact Shards you go into Red.
On Level 8: (Final Boss)
55 Pact Shards you go into Yellow,
115 Pact Shards you go into Orange,
160 Pact Shards you go into Red,
So, you can get between 100 and 110 to keep in yellow and still fight the Last Divinity.