What images of coldness can you find in "The Cold Equations"?

The story is indeed full of imagery expressing the "coldness" inherent in the decision to jettison Marilyn into space. Here's an example:

“And it won’t come back—but there might be other cruisers, mightn’t there? Isn’t there any hope at all that there might be someone, somewhere, who could do something to help me?” She was leaning forward a little in her eagerness as she waited for his answer. “No.” The word was like the drop of a cold stone and she again leaned back against the wall, the hope and eagerness leaving her face. “You’re sure—you know you’re sure?”

The word "no" is likened to the "drop of a cold stone." The lone word is grim in its finality and does little to comfort Marilyn. The decision to jettison Marilyn is a calculated, uncompromising one. The pilot simply tells Marilyn that "there is nothing and no one to change things." Essentially, the softer impulses (such as mercy or pity) will never be part of any scientific equation.
Another example of "cold" imagery is:

They would hate him with cold and terrible intensity, but it really didn’t matter. He would never see them, never know them. He would have only the memories to remind him; only the nights of fear, when a blue-eyed girl in gypsy sandals would come in his dreams to die again . . .

The pilot knows that his decision is based on cold, hard math. Yet, he also understands that Marilyn's parents would never forgive his detachment; he fears that their hatred would be unrelenting, unswerving, and irrevocable in its intensity. 
The text tells us that the laws of nature are "irrevocable and immutable" and that "Men could learn to use them, but men could not change them." Although the pilot can provide logical reasons for jettisoning Marilyn, he knows that her parents will never view his decision as anything other than a vile, merciless move to preserve the status quo. Their hatred towards him will be as "cold" and deliberate as his decision.