Accessibility insights: fixed minor color contrast issues (#5587)

* fixed minor color contrast issues

* go back to using lighten, just use a lower percentage

pxtarget.json

@@ -375,7 +375,7 @@
             "graphBackground": "#d9d9d9",
             "lineColors": [
                 "#6633cc",
-                "#3891A6",
+                "#2C7485",
                 "#3454D1",
                 "#EF767A",
                 "#F46197",

theme/site/globals/site.variables

@@ -9,7 +9,7 @@
 
 @primaryColor: @purple;
 
-@teal: #3891A6;
+@teal: #2C7485;
 @blue: #3454D1;
 @red: #E41B21;
 @pink: #F46197;
@@ -53,7 +53,7 @@
 @simulatorBackground: #FDFDFF;
 @editorToolsBackground: @simulatorBackground;
 @blocklySvgColor: #ecf0f1;
-@cloudCardBackground: lighten(@blue, 9);
+@cloudCardBackground: lighten(@blue, 7);
 
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