Update README.md

README.md

@@ -21,7 +21,7 @@ Build status of the *melodic-devel* branch:
 - C. Rösmann, F. Hoffmann and T. Bertram: Planning of Multiple Robot Trajectories in Distinctive Topologies, Proc. IEEE European Conference on Mobile Robots, UK, Lincoln, Sept. 2015.
 - C. Rösmann, F. Hoffmann and T. Bertram: Kinodynamic Trajectory Optimization and Control for Car-Like Robots, IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Vancouver, BC, Canada, Sept. 2017.
 
-<a href="https://www.buymeacoffee.com/croesmann" target="_blank"><img src="https://cdn.buymeacoffee.com/buttons/lato-orange.png" alt="Buy Me A Coffee" height="31px" width="132px" ></a>
+<a href="https://www.buymeacoffee.com/croesmann" target="_blank"><img src="https://cdn.buymeacoffee.com/buttons/lato-black.png" alt="Buy Me A Coffee" height="31px" width="132px" ></a>
 
 ## Videos