template-safe axis default color inheritance logic

there may be other similar logic we need to update for templates,
but these are the most readily apparent ones

Author: alexcjohnson

src/plots/cartesian/axis_defaults.js

@@ -69,7 +69,9 @@ module.exports = function handleAxisDefaults(containerIn, containerOut, coerce,
     var dfltColor = coerce('color');
     // if axis.color was provided, use it for fonts too; otherwise,
     // inherit from global font color in case that was provided.
-    var dfltFontColor = (dfltColor === containerIn.color) ? dfltColor : font.color;
+    // Compare to dflt rather than to containerIn, so we can provide color via
+    // template too.
+    var dfltFontColor = (dfltColor !== layoutAttributes.color.dflt) ? dfltColor : font.color;
     // try to get default title from splom trace, fallback to graph-wide value
     var dfltTitle = ((layoutOut._splomAxes || {})[letter] || {})[id] || layoutOut._dfltTitle[letter];
 

src/plots/cartesian/tick_label_defaults.js

@@ -27,7 +27,7 @@ module.exports = function handleTickLabelDefaults(containerIn, containerOut, coe
         var font = options.font || {};
         // as with titlefont.color, inherit axis.color only if one was
         // explicitly provided
-        var dfltFontColor = (containerOut.color === containerIn.color) ?
+        var dfltFontColor = (containerOut.color !== layoutAttributes.color.dflt) ?
             containerOut.color : font.color;
         Lib.coerceFont(coerce, 'tickfont', {
             family: font.family,

src/plots/ternary/layout/axis_defaults.js

@@ -25,7 +25,7 @@ module.exports = function supplyLayoutDefaults(containerIn, containerOut, option
     var dfltColor = coerce('color');
     // if axis.color was provided, use it for fonts too; otherwise,
     // inherit from global font color in case that was provided.
-    var dfltFontColor = (dfltColor === containerIn.color) ? dfltColor : options.font.color;
+    var dfltFontColor = (dfltColor !== layoutAttributes.color.dflt) ? dfltColor : options.font.color;
 
     var axName = containerOut._name,
         letterUpper = axName.charAt(0).toUpperCase(),