how to understand "hard" well?
I found that "hard" is a very abstract word. It is very difficult to understand it in different context. Sometimes, you can't find a corresponding definition in the dictionary at all. Here are some examples, could someone explain them?

1. Morning, when the sky was a hard, light blue, I thought of beaches on the Atlantic,......
What does a hard, light blue sky look like?

2. ......But I felt alone between Tom and Juan. I liked that better, anyhow: with Ramon I might have been more deeply moved. But I was terribly hard just then and I wanted to stay hard.
Two "hard" in the sentence.

3. The one questioning me was short and fat. His eyes were hard behind his glasses. He said to me, "Come here."

The three sentences come from the same novel "the Wall".

Thank you.

Question

how to understand "hard" well?
I found that "hard" is a very abstract word. It is very difficult to understand it in different context. Sometimes, you can't find a corresponding definition in the dictionary at all. Here are some examples, could someone explain them?

1. Morning, when the sky was a hard, light blue, I thought of beaches on the Atlantic,......
   What does a hard, light blue sky look like?

2. ......But I felt alone between Tom and Juan. I liked that better, anyhow: with Ramon I might have been more deeply moved. But I was terribly hard just then and I wanted to stay hard.
    Two "hard" in the sentence.

3. The one questioning me was short and fat. His eyes were hard behind his glasses. He said to me, "Come here."

The three sentences come from the same novel "the Wall".

Thank you.

Answer

As you can see,it is indeed very HARD (difficult) to explain this word because it has multiple meanings. Can you have a try at guessing each one from the sentence?
Here is an assignment for you: try to match each meaning of "hard" to one from the dictionary
http://www.thefreedictionary.com/hard

Answer

1. I think the "hard" part refers to how pure the color's hue is, meaning it's very blue, not faded. I've never heard "hard" used like this before. Light hard blue would be the opposite of a light faded blue. Both of those colors are listed on this chart: http://www.speedygrl.com/ctable2.html
2. I'm not sure of the context here. I think the writer means "emotionally hard", as in "unyielding to pressure" emotionally: strong, unmoving, stoic.
3. "Harsh or unfriendly", "stern". 
Hard can be a very abstract concept, but generally, its meanings are very similar to "not soft". (1) The sky was a color blue that was not soft. It was pure blue, not faded. (2) The speaker is not emotionally soft. He/she is closed off and unmoving. (2) His eyes are not soft. They're harsh and unfriendly.

Answer

Hard comes in two form Adjective or as Adverb.....If adjective it would sound different.
If adverb it is referring actions.All these places it is Adjective not referring to any action.