Oh, where to begin?
If there were one thing to teach about using mono, it would be;
IGNORE THE COLOR TILES YOU ARE USING!
Agreeing with almost everything @Halifax has said. It is not about using the color combos which are there. It is about making them. Eliminate the other colors. If there are two horizontal combos available it will do no good to use them immediately. Pull in more by getting rid of others. A reverse thinking much like ghosting. Hard to learn.
Please do give me the wrong color diamond right away. Enemy can only charge to full whether it be 10 tiles or 50. Most likely I will survive their specials early on. Then it is my turn. Hunt and peck off to the side or against an inoffensive opponent. Seems to take forever. Turn a 3 tile into a 4 and odds of winning go way up.
All things being equal, mono is stronger because of the multiplier effect others have mentioned. Based on absolutely nothing but my paranoia, I would suspect there could be anti-stacking software. Four or five of the same color and the number of new tiles for that color is decreased by a % amount. Would require much study.
You do not need a vast roster for mono. I first started doing this with 2* and 3* junk in Wars. Game wants to give me red heroes. (and blue troops. have thrown away 4* blue troops. sigh) Got all this red junk? Fine! Throw it at them. Guess what? yup.
TIP: Use a suicide squad like this in War to practice. and use it when field aid (healing) is in effect against a FULL team. Nothing to lose.
One. combo. at. a. time. will. destroy. any. attack. Period. Having said that, there is nothing 14 combos to the face won’t fix.
Also: If I were picking your team using same color and strength to go up against me, you would lose most every time. duh. You are using hero skills as part of the strategy no matter what color combination is used.
Notice how many people say “I used to do that, now I do this”? That is because the game itself changes with increasing levels. It is not simply a matter of doing the same thing with bigger numbers. Three star tactics do not work at four star level. At some point in time I won 37 consecutive raids. Must have been doing something right. Probably when the second Chao got full. One is just so-so. Two of them rule. Throw in Leonidas and a pair of dark healers and they were unbeatable for a while. I am playing with bigger numbers now but nothing matches that combination.
Titans, Raids, and Alliance Wars are totally different games. Do not compare their results. I do not re-roll or revenge in raids. Try this:
Make a color team. Changing heroes is allowed within that color. Fight all six raid points with that color. Go to next colors. Go to rainbow or some other like 3/2. Then compare results. I do probably below half with rainbow. Usually lose mono because I get stupid or lazy.
Five 5* heroes do not make a team.
I do not use mono against titans (unless it is an easy one) because of time limit. Others say opposite. Am also lousy at using battle items which is big against titans. tornadoes and mana help.
It is not always strong color against center. My red can chew up Boril center like anyone else. Kind of like using blue Boril in events to go against blue reflecting King Arthur. The reflected damage is easily healed and King Arthur ends up killing himself.