If I paste or enter the following into groovyConsole:
def escapeSlash = /The character \/ is a forward slash/
What it displays is a little confusing. It renders in yellow starting at the first forward slash. The intention is that this would show the entire expression, including the terminating forward slash, in yellow.
What it actually does is terminate the "yellow" at the second forward slash, which is escaped.
Fortunately, the expression does execute successfully, but the display makes it seem to the user that there is a syntax error with the expression.