The button with class mw-interlanguage-selector features an SVG with color #707070, but should be Base10 #202122 to be in alignment with button text.
Exemplary button at article https://en.wikipedia.org/wiki/Saint_Eustace
Bring it closer to DSG buttons by
- updating the language icon to be crispier standard icon, not being resized twice by viewport and background-size application
- and by applying a #54595d fill instead of #72777d
- amending the padding (still non-standard),
- adding similar margin to top as underneath the portlet headline to not make "Edit links" link stick on the button
Refraining from changing it further, as the current language list and Vector sidebar doesn't allow a bolder, bigger button.