Here are some useful bits of information about cool and warm hues.  Cool colors recede and warm colors advance.  In landscapes as the atmosphere plays with distant views, soft edges and coolness prevail.  Putting cool next to cool or warm next to warm flattens the appearance, while contrasting cool next to warm adds depth and dimension.  For harmony, pick one temperature as dominate.  And remember, that a color is warm or cool only in reference to an adjacent color.