Cannot load 'colorize'

[ryosa]

With ruby 2.3.1 on CentOS 7, gem 'colorize' cannot be loaded.

[root@hba_ci act]# classy --help
/usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in require': cannot load such file -- colorize (LoadError) from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in require'
from /usr/local/bin/classy:8:in `

'

Gem has been installed.

[root@hba_ci act]# gem which colorize
/usr/local/lib/ruby/gems/2.3.0/gems/colorize-0.8.1/lib/colorize.rb

How can I solve this issue?