Haven't reached a dragon yet but it would be insane dumb if u went against a red dragon (the strongest of chromatic dragons) at level 4. Or even at level 10
LOL.. might want to check your monster manual. Red Dragons come in CR4 and 10 varieties. Meaning they are a speedbump encounter for a party of that level.
I think he means that out of the chromatic dragon types, Reds are the highest CR of the 5. So, if youre looking at all ancients, the Reds are the harder ones.
That being said, its a pretty minor difference and not particularly worth noting as any young is killable by a level 4 party and the Gith don't fly adults. So its a reasonable dragon to have. Its just leveled to 4 and has weird stats, which is the more annoying issues. People tend to inflate the danger of ANY dragon. Theyre tough, and definitely a "fuck, I have to fight a dragon" moments, but by level 5 you can take one without worrying too much. 4 is pretty hard to do, but it is technically possible depending on the group.