Steps to reproduce:
1. Create new Unity project
2. Install Unity AI packages (AI > Agree and Install Unity AI)
3. Make sure Editor theme is set to Light
4. Right-click in Project window > Create > Terrain > Generate Terrain Layer
5. Observe the Refresh button next to “Material Map Assignments” 

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Actual results: “Refresh” button is too light and is difficult to see in Light Editor Theme
Expected results: “Refresh” button should be darker, easer to see when Editor theme is set to Light

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Reproducible with versions: 1.0.0-pre.10 (6000.2.0b3)

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Tested on (OS): macOS Silicon, Sequoia 15.5