now it actually works

plugin/escape_dictionary.vim

@@ -1,25 +1,14 @@
-let s:colorDictionary = {
-    \ 'red':     '31',
-    \ 'green':   '32',
-    \ 'yellow':  '33',
-    \ 'blue':    '34',
-    \ 'magenta': '35',
-    \ 'cyan':    '36',
-    \ 'black':   '30',
-    \ 'white':   '37',
-    \ 'bold':     '1',
-    \ 'italics':  '3',
-    \ 'normal':   '0',
-    \ 'reverse':  '7'
-    \ }
+" NOTE: keys() & values() return their results in arbitrary order
+let s:colorKeys   = ['red', 'green', 'yellow', 'blue', 'magenta', 'cyan', 'black', 'white', 'bold', 'italics', 'normal', 'reverse']
+let s:colorValues = [ '31',    '32',     '33',   '34',      '35',   '36',    '30',    '37',    '1',       '3',      '0',       '7']
 
 function! s:ColorSelected(id, result)
-    let val = '\033[' . values(s:colorDictionary)[a:result] . 'm'
+    let val = '\033[' . s:colorValues[a:result-1] . 'm'
     exec 'normal! i' . val
 endfunction
 
 function! ShowEscapeDictionary()
-    call popup_menu(keys(s:colorDictionary), #{
+    call popup_menu(s:colorKeys, #{
         \ callback: 's:ColorSelected',
         \ })
 endfunction