Color of ocean waters and Ekman pumping - what is the connection?
The relationship of the observed "aquamarine color" near the coast and the Ekman pumping in the open ocean, while possible is rather unlikely. Ekman pumping is confined to the areas affected by the cyclonic wind stress curl and by definition it is mostly effective in the open ocean, where there is no bottom boundary effect. The color of the coastal waters is likely more affected by the upwelling-favorable wind creating upwelling conditions that provide nutrients to the coastal areas. The fact that the color is affected by the sea-breeze is even more justification for the upwelling mechanism. While transport of nutrient-rich waters to the coastal areas is not uncommon, the time scales associated with primary production especially in coastal areas are quite fast and tend to use the open-ocean nutrients in short time scales. 

Phytoplankton changes especially on the order of hours are more likely associated with purely coastal processes. While there might be an input of open-ocean nutrients to the coastal areas, the coastal primary production tends to differ from open-ocean communities and tend to respond rapidly to extra nutrients.

The aquamarine color could be the result of many coastal processes. Without knowing the area, I don't feel qualified to make a strong case about the causes. Reasons for the color could include 1) vertical phytoplankton migrations that settle to the bottom/lower water column when the breeze comes up; 2) the sea breeze resulting on a local near-shore downwelling; 3) a breakdown of the stratification by the breeze that mixes down the surface layers; 4) regional features (e.g., sea level pressure gradient) that become active when the breeze is occurring. Too many unknowns for me. It would be good to know the extent and duration of the "aquamarine color" patch, the width and slope of the continental shelf in the area and the ind and stratification conditions in the near-shore and coastal areas.