So I was inspired to look at which die is the best to add to an attack pool, to optimize attacks.
It turns out the winner is the blue die, up to 4 blue dice, with the runner up as the red dice, again up to 4 dice. Once there are 4 blue dice, black dice become the most valuable.
Now you may be asking how did I determine this?
Simple, I looked at the post-Brace expected damage and the probability of rolling at least one accuracy symbol.
Then I did an iterative assessment between blue and black dice:
6 blue : 4.1 damage
5 blue, 1black : 4.19 damage
4, 2: 4.21 damage
3,3: 4.14 damage
2,4: 3.95 damage
1,5: 3.59 damage
0,6: 3 damage
So, this comes to a somewhat simple rule, assuming you are targeting a ship with one brace token:
Maximize the number of blue dice up to 4. If not blue dice are available, maximize up to 4 red dice, then add blacks.
I just did a quick check, and this holds true even if there are already red dice in the attack pool.
Note the damage increase is small between 3 and 4 blue dice.