Do you mean like a mod or something? The only ingame option is the filter you mentioned. But, yeah, I wish rivers “popped” more since they’re so important to combat, exploration, and city development. If it’s any consolation, you’ll learn to read rivers better the more you play.
It depends on a number of factors, including the difficulty level you’re playing, the nation you’re playing, the families you’re using, and how you’re developing your cities.
Something that’s not immediately obvious is that one of the main sources of science is kind of under the hood: specialists. Science production is a by-product of cultivating your advanced workers (called “specialists”), and not something you develop separately, which is how it works in almost every other strategy game I’ve played. In other words, science kind of “happens” as you develop your economy, regardless of how you develop your economy.
Which is why science structures like libraries and universities don’t add science production; they multiply it.