This won’t work. Here is the main issue:
Custom fields will accept HTML code. So you can use tags to define how text is presented in them. For example, <b>REJECTED</b> produces REJECTED. But a dropdown field’s presentation is not defined by its internal contents the way a single-line field is, but rather by the defined presentation of the field itself, which you cannot control in list views at all. You can control appearance in a finished document by using custom themes. But you would need a lot of looping conditional testing, and you probably don’t want the quote status appearing on the finished document in the first place.
That said, you can do what you ask if you make the custom field a single line. Using only one line at a time of the following HTML code:
<span style="color:red;font-weight:bold">REJECTED</span>
<span style="color:orange;font-weight:bold">PENDING</span>
<span style="color:blue;font-weight:bold">ACCEPTED</span>
<span style="color:green;font-weight:bold">COMPLETED</span>
you can produce a status column in the Sales Quotes list that looks like this:
The problem is that you have to type in all that HTML code every time you want to mark or change status of a quote.