Error in syntax check for simple condition

What causes this issue?

The syntax check found errors in the condition. There are several
possible reasons for this:
Keys (such as characteristic names) that contain hyphens can only be
referred to in dependencies if you enter the keyword SKEY. The key must
be entered in quote marks: SKEY 'EXT-COLOR'
Changes to master data that are made while you are processing a
dependency are not always recognized, due to buffering of data.
Character strings (for example, characteristic values in CHAR format)
must be entered in quote marks: COLOR = 'RED'. Characteristic values in
numeric format are not entered in quote marks.

System Response

The cursor marks the place where the error occurs. There may be a list
of several detailed error explanations for you to select.

How to fix this error?

Check your entry and correct the error. You have the following options
for analyzing and correcting the error:
If you cannot see the error immediately, select a detail message that
looks suitable by choosing the <PF>Details</> pushbutton. The cursor
marks the relevant place in your source code, and you can display the
long text of the detail message for more information, if required. If
the message you selected does not help, you can check again and select
a different detail message.
If changes to master data made while you are processing the dependency
are not recognized, start the dependency maintenance function again.
You can still save your dependency if the source code contains errors.
The status of the dependency is automatically set to <ZH>locked</>, and
the dependency cannot be used for variant configuration.

Error message extract from SAP system. Copyright SAP SE.