Hello A.,
For arrow between `Micro` and `AWS`, you can add a line with only a '|'.
On ditaa the lines (horizontal or vertical) are:
<->
or
^
|
v
That correct also the issue for `thing two`.
Then for color of `AWS`, here is a proposal:
[See code on PlantUML online server]
If that can help,
Regards,
Th.