svg is necessary in monaco.

src/vs/editor/browser/widget/inlineDiffMargin.ts

@@ -56,7 +56,7 @@ export class InlineDiffMargin extends Disposable {
 		this._marginDomNode.style.zIndex = '10';
 
 		this._diffActions = document.createElement('div');
-		this._diffActions.className = 'octicon octicon-light-bulb';
+		this._diffActions.className = 'lightbulb-glyph';
 		this._diffActions.style.position = 'absolute';
 		const lineHeight = editor.getConfiguration().lineHeight;
 		const lineFeed = editor.getModel()!.getEOL();

src/vs/editor/browser/widget/media/diffEditor.css

@@ -94,10 +94,15 @@
 	display: inline-block;
 }
 
-.monaco-editor .margin-view-zones .octicon-light-bulb {
-	opacity: 0.6;
+.monaco-editor .margin-view-zones .inline-deleted-margin-view-zone .lightbulb-glyph {
+	background: url('lightbulb-light.svg') center center no-repeat;
 }
 
-.monaco-editor .margin-view-zones .octicon-light-bulb:hover {
+.monaco-editor.vs-dark .margin-view-zones .inline-deleted-margin-view-zone .lightbulb-glyph,
+.monaco-editor.hc-dark .margin-view-zones .inline-deleted-margin-view-zone .lightbulb-glyph {
+	background: url('lightbulb-dark.svg') center center no-repeat;
+}
+
+.monaco-editor .margin-view-zones .lightbulb-glyph:hover {
 	cursor: pointer;
 }

src/vs/editor/browser/widget/media/lightbulb-dark.svg

+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M11.6708 8.65806C11.3319 8.9916 11.0716 9.36278 10.8886 9.77172C10.7105 10.1792 10.621 10.6219 10.621 11.1009V12.7012C10.621 12.8807 10.5872 13.0503 10.5189 13.2091C10.4513 13.3661 10.3586 13.5038 10.2407 13.6213C10.1228 13.7388 9.98464 13.8311 9.82723 13.8984C9.66806 13.9663 9.49806 14 9.31823 14H7.71205C7.53223 14 7.36223 13.9663 7.20306 13.8984C7.04564 13.8311 6.90753 13.7388 6.78961 13.6213C6.67168 13.5038 6.57895 13.3661 6.51141 13.2091C6.44311 13.0503 6.40927 12.8807 6.40927 12.7012V11.1009C6.40927 10.622 6.31772 10.1795 6.13553 9.77209C5.95683 9.36336 5.69832 8.99156 5.35953 8.65806C4.92468 8.22903 4.58896 7.75003 4.35361 7.22134C4.11756 6.69107 4 6.11672 4 5.49953C4 5.08664 4.05342 4.68802 4.16048 4.30397C4.26728 3.92089 4.41907 3.56286 4.61595 3.23018C4.81257 2.89377 5.04777 2.58911 5.32146 2.31641C5.59503 2.04383 5.89858 1.80953 6.23195 1.61364C6.56979 1.41764 6.93146 1.2662 7.31578 1.15983C7.70106 1.0532 8.10094 1 8.51514 1C8.92934 1 9.32923 1.0532 9.71451 1.15983C10.0988 1.2662 10.458 1.41739 10.7918 1.61351C11.1294 1.80938 11.4351 2.0437 11.7088 2.31641C11.9825 2.5891 12.2177 2.89376 12.4143 3.23016C12.6112 3.56285 12.763 3.92088 12.8698 4.30397C12.9769 4.68802 13.0303 5.08664 13.0303 5.49953C13.0303 6.11672 12.9127 6.69107 12.6767 7.22134C12.4413 7.75003 12.1056 8.22903 11.6708 8.65806ZM9.62162 10.5H7.40867V12.7012C7.40867 12.7823 7.4372 12.8512 7.49888 12.9127C7.56058 12.9741 7.63007 13.0028 7.71205 13.0028H9.31823C9.40022 13.0028 9.46971 12.9741 9.5314 12.9127C9.59309 12.8512 9.62162 12.7823 9.62162 12.7012V10.5Z" fill="#C2C2C2"/>
+</svg>

src/vs/editor/browser/widget/media/lightbulb-light.svg

+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M11.6708 8.65806C11.3319 8.9916 11.0716 9.36278 10.8886 9.77172C10.7105 10.1792 10.621 10.6219 10.621 11.1009V12.7012C10.621 12.8807 10.5872 13.0503 10.5189 13.2091C10.4513 13.3661 10.3586 13.5038 10.2407 13.6213C10.1228 13.7388 9.98464 13.8311 9.82723 13.8984C9.66806 13.9663 9.49806 14 9.31823 14H7.71205C7.53223 14 7.36223 13.9663 7.20306 13.8984C7.04564 13.8311 6.90753 13.7388 6.78961 13.6213C6.67168 13.5038 6.57895 13.3661 6.51141 13.2091C6.44311 13.0503 6.40927 12.8807 6.40927 12.7012V11.1009C6.40927 10.622 6.31772 10.1795 6.13553 9.77209C5.95683 9.36336 5.69832 8.99156 5.35953 8.65806C4.92468 8.22903 4.58896 7.75003 4.35361 7.22134C4.11756 6.69107 4 6.11672 4 5.49953C4 5.08664 4.05342 4.68802 4.16048 4.30397C4.26728 3.92089 4.41907 3.56286 4.61595 3.23018C4.81257 2.89377 5.04777 2.58911 5.32146 2.31641C5.59503 2.04383 5.89858 1.80953 6.23195 1.61364C6.56979 1.41764 6.93146 1.2662 7.31578 1.15983C7.70106 1.0532 8.10094 1 8.51514 1C8.92934 1 9.32923 1.0532 9.71451 1.15983C10.0988 1.2662 10.458 1.41739 10.7918 1.61351C11.1294 1.80938 11.4351 2.0437 11.7088 2.31641C11.9825 2.5891 12.2177 2.89376 12.4143 3.23016C12.6112 3.56285 12.763 3.92088 12.8698 4.30397C12.9769 4.68802 13.0303 5.08664 13.0303 5.49953C13.0303 6.11672 12.9127 6.69107 12.6767 7.22134C12.4413 7.75003 12.1056 8.22903 11.6708 8.65806ZM9.62162 10.5H7.40867V12.7012C7.40867 12.7823 7.4372 12.8512 7.49888 12.9127C7.56058 12.9741 7.63007 13.0028 7.71205 13.0028H9.31823C9.40022 13.0028 9.46971 12.9741 9.5314 12.9127C9.59309 12.8512 9.62162 12.7823 9.62162 12.7012V10.5Z" fill="#424242"/>
+<path fill-rule="evenodd" clip-rule="evenodd" d="M11.6708 8.65806C11.3319 8.9916 11.0716 9.36278 10.8886 9.77172C10.7105 10.1792 10.621 10.6219 10.621 11.1009V12.7012C10.621 12.8807 10.5872 13.0503 10.5189 13.2091C10.4513 13.3661 10.3586 13.5038 10.2407 13.6213C10.1228 13.7388 9.98464 13.8311 9.82723 13.8984C9.66806 13.9663 9.49806 14 9.31823 14H7.71205C7.53223 14 7.36223 13.9663 7.20306 13.8984C7.04564 13.8311 6.90753 13.7388 6.78961 13.6213C6.67168 13.5038 6.57895 13.3661 6.51141 13.2091C6.44311 13.0503 6.40927 12.8807 6.40927 12.7012V11.1009C6.40927 10.622 6.31772 10.1795 6.13553 9.77209C5.95683 9.36336 5.69832 8.99156 5.35953 8.65806C4.92468 8.22903 4.58896 7.75003 4.35361 7.22134C4.11756 6.69107 4 6.11672 4 5.49953C4 5.08664 4.05342 4.68802 4.16048 4.30397C4.26728 3.92089 4.41907 3.56286 4.61595 3.23018C4.81257 2.89377 5.04777 2.58911 5.32146 2.31641C5.59503 2.04383 5.89858 1.80953 6.23195 1.61364C6.56979 1.41764 6.93146 1.2662 7.31578 1.15983C7.70106 1.0532 8.10094 1 8.51514 1C8.92934 1 9.32923 1.0532 9.71451 1.15983C10.0988 1.2662 10.458 1.41739 10.7918 1.61351C11.1294 1.80938 11.4351 2.0437 11.7088 2.31641C11.9825 2.5891 12.2177 2.89376 12.4143 3.23016C12.6112 3.56285 12.763 3.92088 12.8698 4.30397C12.9769 4.68802 13.0303 5.08664 13.0303 5.49953C13.0303 6.11672 12.9127 6.69107 12.6767 7.22134C12.4413 7.75003 12.1056 8.22903 11.6708 8.65806ZM9.62162 10.5H7.40867V12.7012C7.40867 12.7823 7.4372 12.8512 7.49888 12.9127C7.56058 12.9741 7.63007 13.0028 7.71205 13.0028H9.31823C9.40022 13.0028 9.46971 12.9741 9.5314 12.9127C9.59309 12.8512 9.62162 12.7823 9.62162 12.7012V10.5Z" fill="#424242"/>
+</svg>