[css-fonts-4] Clarify parsing rules for the color-<<integer>> descriptors in font palettes

Author: Litherum

css-fonts-4/Overview.bs

@@ -3557,13 +3557,13 @@ The parsing rules for these descriptors are as follows:
 
 1. The descriptor must start with the string "color-".
 
-2. If there is nothing remaining in the string, it is a parse failure.
+2. If there is nothing remaining in the string, the descriptor is invalid.
 
-3. Otherwise, if the next character is a 0, the presence of anything after the 0 results in a parse failure.
+3. Otherwise, if the next character is a 0, the presence of anything after the 0 results in an invalid descriptor.
 
 4. Otherwise, if the next character is a non-zero digit (1 through 9), the remainder of the string must be digits.
 
-5. Otherwise, it is a parse failure.
+5. Otherwise, it is an invalid descriptor.
 
 Using these rules, the non-negative integers prefixed with "color-" are valid identifiers.