Colorful Harvest is pretty much a hentai manga that isn't actual hentai.
Story and characters would be really good for a H title, but as it isn't one, I'm going to rate them as non-H manga, which means low. I mean, this is just hentai without directly shown genitals. The only purpose of story is to show sex scenes. Characters also don't have any depth or reason behind their behavior.
On the bright side protagonist pick a girl in the end and we get actual satisfying ending.
Art is good. Sex scenes are drawn really well and characters look great. It lacks in other fields, but for this kind of manga it's fitting.

Generally speaking, if it was a hentai manga, it'd be one of the better ones. But as a seinen ecchi/romance title, it is just weak. On the other hand it's short and "pleasant" to read, if you know what I mean. While I wouldn't actively recommend this manga, I wouldn't say it's not worth reading.