I've had both calculators, and I honestly can't recommend spending extra for the color one. The main change made to the TI-84+ is that it can make graphs in color (Gee, really? Who'da thunk it?

). This can sometimes be useful if you're trying to compare multiple graphs on the same plot, as trying to do so in black and white is hard. The regular TI-84 will draw multiple graphs in different patterns, but I find them very difficult to distinguish.

Aside from that, I only noticed two other changes: The color version has a bigger screen and uses its own rechargeable batteries, whereas the regular TI-84 uses two AA's. I did enjoy the bigger screen, but I just don't think it's worth the extra $21. And unless you plan on using your calculator for a very long time such that the expense of buying batteries would add up, I don't see how that could be worth it either. When I was heavily using my calculator for math classes, I recharged the battery on my TI-84+ about once every two months, and I changed the batteries in my regular TI-84 about every three months.

However, TI does make two other types of calculators that might be worth splurging for, though I've not personally used either one and I don't know how much they cost. The TI-89 Titanium and the TI-Nspire CX both have computer algebra systems, meaning they can compute and calculate symbolic representations, such as telling you that \(\displaystyle \displaystyle \int x^2 \: dx = \frac{1}{3}x^3 + C\) rather than only being able to compute definite integrals like the TI-84/+ can. Here's some links to information pages about these calculators, from TI's website.