fix: improve bar chart color contrast (#71)

Author: Boshen

apps/dashboard/src/RolldownStats.tsx

@@ -111,7 +111,7 @@ function RolldownStats({ selectedMetric, setSelectedMetric }: RolldownStatsProps
 
   const rolldownMetrics = [
     { id: 'bundleSize', name: 'Bundle Size', icon: Package, data: bundleSizeDiffData, color: '#374151' },
-    { id: 'buildTime', name: 'Build Time', icon: Clock, data: buildTimeData, color: '#000000' },
+  { id: 'buildTime', name: 'Build Time', icon: Clock, data: buildTimeData, color: '#2563eb' },
   ];
 
   const currentMetric = rolldownMetrics.find(m => m.id === selectedMetric) || rolldownMetrics[0];
@@ -234,8 +234,8 @@ function RolldownStats({ selectedMetric, setSelectedMetric }: RolldownStatsProps
                   </Bar>
                   <defs>
                     <linearGradient id='buildTimeGradient' x1='0' y1='0' x2='0' y2='1'>
-                      <stop offset='0%' stopColor='#000000' stopOpacity={1} />
-                      <stop offset='100%' stopColor='#374151' stopOpacity={0.8} />
+                      <stop offset='0%' stopColor='#2563eb' stopOpacity={1} />
+                      <stop offset='100%' stopColor='#3b82f6' stopOpacity={0.8} />
                     </linearGradient>
                   </defs>
                 </BarChart>