I found two simple solutions to this problem:
1) Create a new file and add the following lines:
file_export_version=3.0 /instance/org.eclipse.ui.workbench/org.eclipse.cdt.ui.ColoredLabels.match_highlight=128,0,128
You can change the color value to suit your theme.
Then go to File β Import β Settings
Browse to the newly created file and click Finish.
2) Go to [workspace-location] /. metadata / .plugins / org.eclipse.core.runtime / .settings
Modify the org.eclipse.ui.workbench.prefs file and add the line
org.eclipse.cdt.ui.ColoredLabels.match_highlight=128,0,128
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