I'm partial for statues, and birds and rivers is a good theme. I feel like if they sticked to the semi-monochrome of the previous notes I'd be more favorable to them aswell. Monochrome might be the wrong word, ESL.

For reference, the two previous runs at the top of the page: https://en.wikipedia.org/wiki/Euro_banknotes

Monochrome means "single colour". Typically shades of that colour are included, so if something was dark purple lines on a light purple background we might say that's monochrome. In some cases it's taken to mean that there's just black/ grey/ white, but here it makes sense to say that e.g. one note is green, another blue, but no individuals notes are a mix of green and blue, they're monochrome.

Since you mentioned English isn't your first language, this use of the "to stick" verb where it's about adhering to something (metaphorically in your case) has a different past participle, "stuck". You wrote "sticked" which makes sense but isn't used for this meaning today. Nobody will misunderstand but it will sound wrong to them, we'd say e.g. "Perhaps if we'd stuck with Zig the game would be finished by now" or "Somebody stuck their chewing gum to the table".

Most of these new designs are monochrome excepting that the European flag is itself blue because that's what colour the flag is. A few of them are more colourful, and I see what you mean about that adding to clutter. For their purpose they're successful because the big reason to use colour is that people with very poor sight (some of whom are legally blind but do retain some ability to determine colour) can tell a red note from a blue one, the small accents in a different colour won't affect that. If your sight is good enough to figure out it's a European flag, you don't need this cue, you can read the large numerals saying "100" nearby to determine it's a €100 note.