Removed hard-coded colors in my zsh theme

Now I can use the theme in light terminal themes. Before this, it always
showed a black background in the in the prompt, which looks horrible in
light themes.

zsh/.zsh-custom/prompt_balkian_setup

@@ -6,7 +6,7 @@
 #
 # Authors:
 #   Isaac Wolkerstorfer <i@agnoster.net>
-#   Jeff Sandberg <balkian460@gmail.com>
+#   Jeff Sandberg <paradox460@gmail.com>
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 # Screenshots:
@@ -47,11 +47,11 @@ function prompt_balkian_end_segment {
 }
 
 function prompt_balkian_build_prompt {
-  prompt_balkian_start_segment black default '%(?::%F{red}✘ )%(!:%F{yellow}⚡ :)%(1j:%F{cyan}⚙ :)%F{${hostnamecolor}}%n%F{white}@%F{${hostnamecolor}}%m%f'
-  prompt_balkian_start_segment black default '$_prompt_balkian_pwd'
+  prompt_balkian_start_segment default default '%(?::%F{red}✘ )%(!:%F{yellow}⚡ :)%(1j:%F{cyan}⚙ :)%F{${hostnamecolor}}%n%F{white}@%F{${hostnamecolor}}%m%f'
+  prompt_balkian_start_segment default default '$_prompt_balkian_pwd'
 
   if [[ -n "$git_info" ]]; then
-    prompt_balkian_start_segment black yellow '${(e)git_info[ref]}${(e)git_info[status]}'
+    prompt_balkian_start_segment "" yellow '${(e)git_info[ref]}${(e)git_info[status]}'
   fi
 
   prompt_balkian_end_segment