As described in this issue Fanael/rainbow-delimiters#40 if you have configured evil-mode and rainbow-parens to be always on, upon buffer launch you enter normal state of evil mode, and you see parens are not rainbow-colored, unless you enter insertion state of evil mode. I tried with other themes and they all worked fine, for example: cyberpunk theme, spacemacs theme.
As described in this issue Fanael/rainbow-delimiters#40 if you have configured evil-mode and rainbow-parens to be always on, upon buffer launch you enter normal state of evil mode, and you see parens are not rainbow-colored, unless you enter insertion state of evil mode. I tried with other themes and they all worked fine, for example: cyberpunk theme, spacemacs theme.