Describe the bug
Thanks to #1397 there is a way to specify the colours used in the jq output, but it's not possible to change the FIELD_COLOR (used for dictionary keys for example).

To Reproduce
JQ_COLORS="1;30:0;31:0;32:0;33:0;34:1;35:1;36" ./jq -Cn '[{"a":true,"b":false},123,null]' [{"a":true,"b":false},123,null]

Expected behavior
Another field in the env var to override the color of field names.

Environment (please complete the following information):

• OS and Version: macOS 10.14
• jq version 1.6rc1