+ background color on region markers

Inheritance.md

@@ -87,7 +87,7 @@ A closed shape would fail because any candidate node would have more than e.g. `
 }
 ```
 
-![](https://placehold.it/350x40/fff/070?text=<HS>)
+![](https://placehold.it/350x40/fec/070?text=<HS>)
 
 The above example is a bit difficult to understand.  How about:
 ```
@@ -97,7 +97,7 @@ The above example is a bit difficult to understand.  How about:
 A ShEx interpreter worth its salt would be able to identify the above as an error -- the set of possible graphs that could satisfy 
 <ExtendedLonelyBox> is empty.  Same thing as the previous example, however.
 
-![](https://placehold.it/350x40/fff/070?text=</HS>)
+![](https://placehold.it/350x40/fec/070?text=</HS>)
 
 Likewise, a repeated property:
 ```
@@ -135,7 +135,7 @@ This means that a node which conformed to a derived shape, e.g. `<PosturedBP>`:
 ```
 would not conform to a base shape `<BP>` which accepts only two `:components`.
 
-![](https://placehold.it/350x40/fff/070?text=<HS>)
+![](https://placehold.it/350x40/fec/070?text=<HS>)
 
 This is desired behavior from my perspective, at least for one interpretation of "inherits".  A useful interpretation of:
 
@@ -198,7 +198,7 @@ are also instances of
 ```
 To act as a constraint -- this may be a tall order, however.
 
-![](https://placehold.it/350x40/fff/070?text=</HS>)
+![](https://placehold.it/350x40/fec/070?text=</HS>)