Nothing. Light or dark dashboards are more of trends in specific areas, such as Business Intelligence. The industry have moved from light dashboard to dark dashboard without a clear spence of what it may or may not communicate to users. Instead dashboard developers say two things matter: mobile devices and competitors. Not communication with users.
Business Intelligence could be RPGs complete opposite in terms of audience, when and where its dashboards are used and still implementing dark color design.
Stephen Few, author of the book Information Dashboard Design: The Effective Visual Display of Data, also address the use of color in his white paper Common Pitfalls in Dashboard Design.
PITFALL #12: MISUSING OR OVERUSING COLOR
Color can be used in powerful ways to highlight data, encode data, or create a relationship between individual items on a dashboard, but it is commonly over-used and misused. Color choices must made thoughtfully, based on an understanding of how people perceive color and the significance of color differences. Some colors are hot and demand our attention while others are cooler and less visible. When any color appears as a contrast to the norm, our eyes pay attention and our brains attempt to assign meaning to that difference. When colors in two different displays are the same we are tempted to relate them to one another. We merrily assume that we can use colors like red, yellow and green to assign important meanings to data, but in doing so we exclude the 10% of males and 1% of females who are color blind.
A common problem is the use of too many colors, especially bright colors. Because dashboards are often densely packed with information, the visual content must be kept as simple as possible. The use of too many colors can be visually assaulting. When overused, color loses its power to highlight what’s most important.
(...) Nevertheless, time is wasted as our brains—whether consciously or unconsciously—search for the nonexistent meaning of these differences. It is best to keep colors subdued and neutral, except when you are using color to highlight something as especially important.
Light or dark dashboard doesn't intend to communicate anything, but good use of dashboard color can be great for users if the information presented is accurate, relevant and appealing.