In Version 1903 they changed the default Light color mode to light grey, but this color can be changed by going into Settings > Personalization > Colors and changing the top dropdown menu labeled "Color" to Custom mode. Below that change the Default Windows
Mode to Dark, which now includes colors. (I would hold off on also choosing Dark theme for Default Apps Color because for some it's turning it black, which may be a bug).
Once you do that choose an Accent color from the color palette, or tick the box to Pick an Accent color from your Background. Below that tick the box to Show Accent Color on Start, Taskbar and Action Center and Title Bars and Windows borders.
This is further illustrated in this tutorial: How to change color modes on the Windows 10 May 2019 Update | Windows Central
For example, when I choose Custom colors for Windows and Apps, then check the boxes for Transparency (more an enhancement than transparent) and Pick a Color from my Backgrounds, apply it to Taskbar, Start Menu and Title Bars & Windows, it gives a dark colored task bar and Windows frames, a slightly less dark colored Start Menu, and more brightly colored apps - all in a color theme it's selected from my desktop slideshow Theme - today it's been blue, aqua, brown and green. But you can customize this to any other color or combination from the color palette.
For Themes I use the spectacular free slideshow Themes from the Store that will install to the Personalization > Themes panel to choose from: Windows Themes - Microsoft Store
Note if you choose a new Theme you'll need to redo the above steps afterward.
To change text color to another or back to black if necessary see here:
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