Color blind friendlier icons
Both Overview and History depends on colors to show high and lows. This works well for many users, but for many these colors all look the same! Use symbols as well as colors to represent values.
Lows should use ▲ for hypoglycemia, △ for highs, ▼ for lows, and ● for regular values. These symbols are commonly used in other diabetic software and are quite self-explanatory.
Red/green color blindness is the most common variant so using those two colors is generally a bad idea.