Ke rui - yes, you can get those results in two ways; either by tapping on the "Full" button below the search input field (when it's open) to search in full-text mode, in which case the C-E entries containing that word would show up right away, or (beginning in 2.0.7) by going into Settings / Dictionary / Search Types / Full-text and enabling "Include in E-C srch", in which case you could switch to searching for that word in C-E dictionaries along with E-C ones seamlessly by tapping on the dictionary switch button. (bit hard to explain, so I'd suggest upgrading to 2.0.7, enabling that option, then cycling through all of your dictionaries to try it out)
estudiando - no particular convention, they're just the colors my friend Sam Lipoff (who came up with / pitched me the idea for tone coloring way back in 2001) used in his original paper-based prototype and he based them on the four colors of pen he happened to have available. Though it seems sensible enough - keeping R/G/B for the first three colors might make them easier to remember for some people at least, and associating the similar 2nd/3rd tones with "cool" colors and 1st/4th tones with "warm" colors is also very logical. John Pasden (of ChinesePod fame) had an article about tone colors on his blog at
http://www.sinosplice.com/life/archives/2009/08/11/tone-and-color-in-chinese - his proposed scheme is similar, keeps the cold/warm distinction for 2/3 / 1/4 and uses the same colors for 2/3, but he makes 4th tone red and 1st tone orange. Which I suppose makes more sense - 4th is really more deserving of the "hottest" color - though orange doesn't show up that well on computer screens (particularly not in daylight).
Anyway, there are a lot of different strategies for this, which is why we make the tone colors customizable - we've already gotten about half a dozen emails with proposed alternate coloring schemes, changing our defaults would probably be a bad idea (people wouldn't know how to get back the colors they were used to) but we're thinking about including a built-in list of color schemes that people can choose from without having to fiddle around with the color picker. We'd actually love to use the tone colors in other parts of the UI too if we can - stick them around the borders of flashcards, say, to see if people would pick them up better peripherally / subconsciously than by staring directly at them in the headword characters.
UNI alternate fields are still in the pipeline, just didn't get to it in this release - after we finish the mad dash to flashcards, you're going to see a
ton of cool little things like this added (both on iPhone and on WM) in the next few releases that follow them.