I put blue and green nail polish on alternate fingers.
I gave myself a manicure in alternate colours of blue and green.
ーI put blue and green nail polish on alternate fingers.
「青と緑のマネキュアを交互の指に塗った」
on alternate fingers で「交互の指に」
ーI gave myself a manicure in alternate colours of blue and green.
「青と緑を交互にマネキュアを塗った」
to give oneself a manicure で「マネキュアを塗る」
in alternate colours of blue and green で「青と緑を交互に」
ご参考まで!