...
http:
//YOURDOMAIN
/plugins/servlet/crm/api?command=adddictionaryvalue&userName=${userName}&apiKey=${apiKey}&dictionaryName=Colors&newvalue=Green
Remove value "Green" from the custom dictionary "Colors"
http:
//YOURDOMAIN
/plugins//YOservlet/crm/api?command=removedictionaryvalue&userName=${userName}&apiKey=${apiKey}&dictionaryName=Colors&valuetoremove=Green
where:
${apiKey} - key's title API Key (password) in the Administration/Plugins/CRM/Access
${userName} - JIRA user's login