If the use of the red cross emblem was a mistake or not is open to debate, but it is not a war crime. The Legal concept of Exigent Circumstances was created just for cases like this.(sometimes lawyers do good stuff) Exigent Circumstances will allow Law Enforcement to violate other laws,rules,and procedures in situations where there is an extreme risk of loss of life. Freeing hostages would qualify.

Further if it was a mistake,that does not require the Columbian Government to discuss it in public. (Having a no comment policy is the same as pleading the 5th in this country) They could have seen the Red Cross in private.