<p><b>@stefanb</b> commented on this pull request.</p>

<hr>

<p>In <a href="https://github.com/openstreetmap/openstreetmap-website/pull/1779#discussion_r172483571">app/helpers/browse_helper.rb</a>:</p>
<pre style='color:#555'>> @@ -188,4 +190,16 @@ def telephone_link(_key, value)
 
     "tel:#{value_no_whitespace}"
   end
+
+  def colour_preview(key, value)
+    return nil unless (key =~ /^(|building:|ref:|roof:)colour$/ || key =~ /^(int_)?ref:colour(_(bg|tx))?$/) && !value.nil?
</pre>
<p>If we just look at the existing data and disregard the wiki, we should</p>
<ul>
<li>also make the "u" in "colour" optional. - <a href="https://taginfo.openstreetmap.org/search?q=color" rel="nofollow">https://taginfo.openstreetmap.org/search?q=color</a></li>
<li>allow any optional prefix and suffix, not requiring any special separators</li>
<li>drop the case sensitivity</li>
</ul>
<p>Which makes the regex boild down to simple:</p>
<pre><code>/colou?r/i
</code></pre>
<p>which can be understood that the editor wanted to tag some colour property and if the value indeed looks like a colour (hex code or valid w3c value) we can provide the preview.</p>
<p>Or we could require some common key structure. According to <a href="https://taginfo.openstreetmap" rel="nofollow">https://taginfo.openstreetmap</a><br>
require some common key structure. According to <a href="https://taginfo.openstreetmap.org/search?q=colour" rel="nofollow">https://taginfo.openstreetmap.org/search?q=colour</a> we could generalize it to:</p>
<ul>
<li>alow any optional prefix, separated by colon (:) or underscore (_)</li>
<li>allow any optional suffix, separated by colon (:) or underscore (_)</li>
<li>insist on british spelling with "u"</li>
<li>require lowercase</li>
</ul>
<pre><code>/^(.+[:_])?colour([:_].+)?$/
</code></pre>
<p>Both generalizations would allow us to preview all sorts of future colour tags, even unforeseen enforcements:<br>
<a href="https://user-images.githubusercontent.com/319826/37027467-a363018e-2131-11e8-926d-bce7edf77343.png" target="_blank"><img src="https://user-images.githubusercontent.com/319826/37027467-a363018e-2131-11e8-926d-bce7edf77343.png" alt="image" style="max-width:100%;"></a></p>
<p>What level of generalization did you have in mind?</p>
<ul>
<li>any tag or any tag that looks like it is related to colour</li>
<li>any structure or some specific separators</li>
<li>any spelling (british or us also)</li>
<li>any case (upper, lower, whatever)</li>
</ul>

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