Offensive Buffs and Color Stacking
When many intermediate players of empires and puzzles look at the high titan scores of their alliance team members, they may wonder how they got them. Usually two things play a role:
Luck
Multiple attack Stacking (colors and buffs)
This post shows how tile damage increases dramatically with multiple heroes buffed up.
Damage Model
While I have no idea what the game uses to calculate observed damage, as of v1.10.2 the following model worked pretty good. No a model is predictive, but may not be 100% accurate, this model will help for explaining color stacking in more detail.

Notes
Troops multiple the base damage and attack by a value
Actual tile damage a single tile/shield does is the calculated value above divided by three (irrespective of how many tiles are sent to the enemy).
"Strong" tile attacks are double the value calculated above (modified for tiles as needed). Note specials don't appear to be strong or weak (e.g. a green special on red hero does not appear to be 1/2 of the expected value).
"Weak" tile attacks are half the expected value
Critical damage for attacks are double the normal value
Critical damage from hitting the weak point on a titan is 50% more than the expected value.
Attack Examples
So a fully leveled Wu Kong with my troops below will have the following attack and defensive stats:

Attack --> 841 = 707 x (1+ 0.19) ... That is the base attack (707) with the troops providing a 19% attack bonus.
Defense --> 694 = 620 x (1+ 0.12) ... That is the base defense (620) with the troops providing a 12% defense bonus.
And if this Wu Kong attacked itself; the damage could be calculated as follows.

Or about 40 hit points per tile.
Color Stacking (Use Two Wu Kongs)
First Primer for Color Stacking. What if my offensive team consisted of 2 of these Wu Kongs and raided a defensive team oddly was composed of only these two Wu Kongs. Since the offensive teams stack and the defensive teams don't, my damage would could be estimated as follows:

Or about 70 hit points per tile, not quite double, but a real big improvement.
Real Battle Damage
Here are some screen shots for a battle with a 8* Purple titan. Note that defensive teams (Raids / Alliance Wars) don't benefit from this color stacking. They actually allow the
Original Damage
The follow shows the damage against the titan for yellow heroes without any buffs.

Each tile was doing 340ish damage against this titan with 1.5x for hitting the weak
48% attack Buff
The follow shows the damage against the titan for yellow heroes without any buffs.

Wu Kong Rules
The following shows the total devastation from stacking and Wu Kong hitting a titan. Note that there is also the +48% attack on two of the yellow heroes.

For reference, red tiles hit at ~200 a piece (in the critical spot, or 133 a piece elsewhere).