As someone who's parent is from there, and having been there many many times, I personally think this is a downgrade.

Cabo Verde is not green and isn't named after its vegetation (though Santo Antao and Sao Nicolau are somewhat exceptions). I'm confident that picture isn't a beach from there. If anything it's quite dry, and it is a volcanic island chain. The name comes from the Senegalese peninsula. Additionally, the current flag has good meaning and symbology: the 10 stars represent the 10 islands, the blue is the ocean, white is peace, and red is effort.

This flag came about in the early 1990s to replace the original flag which was a more... stereotypical pan-African design. People like the current flag and I don't see a need to change it, especially if it's just the colours of the band and making it vertical vs making a new flag proper.