ruby syntax error, unexpected ':', expecting keyword_then - ruby-on-rails

Question

I've recently updated ruby from 1.8.7.374 to 2.1.2p95 and I have a svn post-commit script which was working fine but now it fails.
changes=`#{svnlook} diff #{repo} -r #{rev}`
body << "<pre>"
changes.each do |top_line|
top_line.split("\n").each do |line|
color = case
when line =~ /^Modified: / || line =~ /^=+$/ || line =~ /^## /: 'gray'
when line =~ /^-/ 'red:'
when line =~ /^\+/ 'blue:'
else "black"
end
body << %Q{<font style="color:#{color}">#{CGI.escapeHTML(line)}</font> <br/>\n}
end
end
body << "</pre>"
Here's the errors I get:
[root#dev hooks]# ruby -c post-commit
post-commit:66: syntax error, unexpected ':', expecting keyword_then or ',' or ';' or '\n'
...ne =~ /^=+$/ || line =~ /^## /: 'gray'
... ^
post-commit:67: syntax error, unexpected keyword_when, expecting keyword_end
when line =~ /^-/ 'red:'
^
post-commit:67: syntax error, unexpected tSTRING_BEG, expecting keyword_end
when line =~ /^-/ 'red:'
^
post-commit:68: syntax error, unexpected keyword_when, expecting keyword_end
when line =~ /^\+/ 'blue:'
^
post-commit:68: syntax error, unexpected tSTRING_BEG, expecting keyword_end
when line =~ /^\+/ 'blue:'
^
post-commit:69: syntax error, unexpected keyword_else, expecting keyword_end
else "black"
^
post-commit:65: warning: assigned but unused variable - color
post-commit:18: warning: assigned but unused variable - saddress
post-commit:20: warning: assigned but unused variable - sendmail
post-commit:73: syntax error, unexpected keyword_end, expecting end-of- input
Any help in solving this is much appreciated.

Answer 1

Since Ruby 1.9, case expressions don't allow a colon anymore (cf. this answer).
To fix it, change your code to
color = case
when line =~ /^Modified: / || line =~ /^=+$/ || line =~ /^## /
'gray'
when line =~ /^-/
'red:'
when line =~ /^\+/
'blue:'
else
"black"
end

Answer 2

Error in line: when line =~ /^Modified: / || line =~ /^=+$/ || line =~ /^## /: 'gray', as error message mentioned. Just remove : after /^## /.