I'm getting ~ character when I try to change my nickname colors

[22:07:02 INFO]: [world]<_WyRe_> asd
[22:07:13 INFO]: _WyRe_ issued server command: /nick &5_WyRe_
[22:07:14 INFO]: [world]<~_WyRe_> asdasd

Works as intended. If you set ANY nickname with the /nick command (even if you change the colors only), Essentials applies a prefix to the nickname. This settings is defined in Essentials's config.yml.

nickname-prefix: '~'

If you want to disable the prefix, set nickname-prefix: ''