I disagree with some of that.
BT needs to be with every titan. I’ve tried leaving him out vs blue and damage goes down, assuming you’re smart about using your specials. Also, BT, Wu Kong, and Tibertus should come in vs every titan, regardless of color. The combination of BT’s buff, Tib’s defense debuff, and WK attack buff is where most of your damage comes from.
In general people bring 2-3 of the color that’s strong vs the titan because the tiles are 2x damage and take out the weak color hero because they only do 50% tile damage (unless they have a necessary special like Tibertus).
having said that, here’s what I’d do with each color titan (assuming those 4* heroes are all max 70)
Blue: BT Wu Tibertus Caed Skittle
Red: Blue: BT Wu Tibertus Boril X (X = your highest attack 3* max 50 blue like Ulmer…if none Hu Tao)
Green: BT Wu Tibertus <next highest red 3* assuming it’s max) Caed
Purple: BT Wu Tibertus Hu Tao Caed
Yellow: BT Wu Tibertus Caed <next highest purple 3* assuming max 50>