Depending on the used theme, it is possible that the default colors of the icons do not enough contrast. Fortunately, this can be changed easily. 


Select the DBGrid component and open the fields property.


In the edit and delete field, you will see a link like: <i class="fas fa-trash text-dark"></i>


Remove 'text-dark' , click ok and generate/run the application. (By using the bootstrap colors like text-primary etc, you can also change color).