When the colon introduces a complete sentence, some people capitalize the first letter -- not all, though. My English teachers never said we had to do that. So, I think it's a style issue.
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CliveHi,You wrote "I'd go farther..." Shouldn't it be 'further'?
I'd go farther, and say that capitalizing after a colon is incorrect, except in special cases like a proper noun or a colon that introduces direct speech.
Best wishes, Clive