Summing up the information on the comments, the problem you are having is that your background doesn't allow for much contrast, because it's neither too dark nor too light.
Contrast is the difference in visual properties that makes an object (or its
representation in an image) distinguishable from other objects and the
Ideally, you should work with backgrounds that allow for more contrast (dark grey - white text, white - dark text). Contrast is essential for readability.
This tool can help you test your colors so you have a good contrast. For your particular color, since it falls right in the middle (it's not too dark or too light), white or black are the best contrast options (4.7 and 4.5 respectively).
We can't really suggest colors as it would depend on the taste of your client alone. Give that tool a try, prepare some samples and pick one that is both aesthetically pleasing and allows for the text to be highlighted.