You need an embassy visa for United Kingdom if you have a Colombian passport
Visa options for United Kingdom
Visitor visa
Travellers need a visa to visit United Kingdom for Business or Tourism. A paper or embassy visa is the only visa available for travellers visiting United Kingdom. The visa is typically a stamp or sticker added to the passport. Travellers must obtain this visa from a local embassy, consulate, or visa center before travelling. See the source for more details.
This is not offered by sherpa°.
Apply on the government site.