title: How can I color the ocean blue in a map of the US?
body: <p>I would like to draw a map of the US over an image, but then fill in the oceans.</p>
  
  <p>here is my starting point:</p>
  
  <pre><code>library(maps)
  library(graphics)
  image(x=-90:-75, y = 25:40, z = outer(1:15, 1:15, "+"), 
        xlab = "lon", ylab = "lat")
  map("state", add = TRUE)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/WYfF4.png" alt="enter image description here"></p>
  
  <p>But I would like the Atlantic Ocean and Gulf of Mexico to be filled in a solid color.</p>