You can get the element color(Background color of element) by:
element.getCssValue("background-color");
You can get the element text/caption color by:
element.getCssValue("color");
For example if you want to get the background and text color of "Sign in" button for LinkedIn, the code is as follows:
driver.get("https://www.amazon.com/");
String buttonColor = driver.findElement(By.id("searchDropdownBox")).getCssValue("background-color");
String buttonTextColor = driver.findElement(By.id("searchDropdownBox")).getCssValue("color");
System.out.println("Button color: " + buttonColor);
System.out.println("Text color " + buttonTextColor);