Final answer:
To correct the given sentence by inserting a comma, the correct sentence would be: 'Wow, Yellowstone's Grand Prismatic Spring sure is colorful!'.
Step-by-step explanation:
The sentence 'Wow Yellowstone's Grand Prismatic Spring sure is colorful!' requires a comma to separate the introductory expression 'Wow' from the rest of the sentence. The correct sentence would be: 'Wow, Yellowstone's Grand Prismatic Spring sure is colorful!'. The comma helps to indicate a pause and separate the exclamation from the subject of the sentence.