The way I would do that is to create a dedicated button for this purpose. When editing a card on AnkiDroid, on the very right of the bottom toolbar you should see a + icon:
If you press it the dialog for making a button will show up. In the first field, you’ll need to enter a name the button will have on the toolbar. It should be short, so emojis are good for this purpose (like the 
on the image above, or for coloring you might want to use something like 
). In the second field, you put this piece of code (you can choose the value for color the same way I described in the previous post):
<span style="color: #886ce4">
and in the last field this one:
</span>
After clicking Create the button should appear on the toolbar, and you’ll be able to use it to color any selected part of text (it won’t look like this in the editor – it will display the source code – but during reviews/previews or in the desktop editor you’ll see the words accordingly colored).
Keep in mind, however, that I don’t often use AnkiDroid myself, so a better solution which I’m simply not aware of might exist. You might want to ask about it in the respective forum thread, where people more knowledgeable about this stuff will be able to help you: AnkiDroid (Android) - Anki Forums
Try following these steps: GitHub - Eltaurus-Lt/Anki-Card-Templates: Decks of templates + source code for Anki cards (I’m assuming that you have Anki desktop as well since you were able to modify the template earlier). It is a good idea to create a backup (File → Create Backup) before doing such significant changes to your collection, so that you would always be able to easily revert back in case anything goes wrong.