PLEASE! At least just give us the option/possibility to change the color of the trace line (separately from changing the entire theme). This is by NO means an outrageous or unreasonable request!
If full customization (like a wheel or sliders) are "too much" to ask, provide a selection of a few colors (besides orange)! There are numerous posts expressing dislike, disdain, disgust and aversion to the nauseating color that was for some reason adopted by Swype some years ago (what was wrong with the original aqua bluish color? I liked that, it was nice...

It was nice that that you finally gave us some themes. But the selection and variation is rather pathetic! And it would've been SO MUCH better to provide the options to change some of the components individually- even if only offering 2-4 selections for each!

What I have in mind is the ability to change the following aspects of the theme separately:

the trace line & 'default' suggestion color (at least one color in the green to violet range please!)
the background color of the theme (perhaps: light, dark and classic)
whether or not the long-press characters are displayed

Separate control of those elements would be fantastic, and could be easily accomplished while maintaining a simple, intuitive interface.

Thank you so much!!!

Even more settings could be made available for advanced users on another screen (perhaps protected by a warning)... ideas for detailed controls:
complete separate control of the color & opacity (meaning: RGBa sliders or comparable alternative) of each component: main background, key/button background, key/button outline, main letter/number/character, secondary (long-press) letter/number/character, word suggestion area background, default/primary word suggestion, additional/secondary word suggestions
when viewing the special (non-letter) characters 'pages', give option to display (and access via long-press) the characters on the other page of non-letter characters in a smaller size (just like how the long-press characters are displayed on the main keyboard 'page' showing the alphabet)
option to change the font & size (individually... for the main characters, the smaller long-press characters, as well as word suggestions/predictive text)