Monosyllabic colors names (e.g. 红, 蓝) as predicates with and without 色
1， “Adj 不 Adj?” is just a short form for &quot;是不是 Adj 的?&quot;
For example, I drink a lot of wine and want to know if my face turns red, so I ask my friend.
Q: &quot;我的脸红不红？&quot;
A: &quot;你的脸很红。&quot;

2， &quot;adj 吗&quot; is an even shorter form.
Q: &quot;我的脸红吗？&quot; A：“你的脸很红。”

3， 红 can also be a verb but that means &quot;turns red&quot;, there must be a transition.
Q: &quot;我的脸红没红？&quot;
A: &quot;你的脸红了。&quot;
Ref:
zdict 紅〈动〉(1)