Dropdown inputs on issues is difficult to read

Summary

Input fields for issues have a text color of rgba(0,0,0,0.85); but the dynamic dropdowns for Assigne and other fields have a text color of rgba(0,0,0,0.55);.

I find these faint colors difficult to read. Especially for the milestone fields which often contains just a number value.

Steps to reproduce

Create a new issue. Enter text in all the input fields. Compare the text color of input fields for consistency.

What is the current bug behavior?

Appears to be a style issue with the dropdown .selectbox control.

What is the expected correct behavior?

When no value is selected, the text color should be $placeholder-text-color (#949494).

When a value is entered into the dropdown, the text color should be changed to $gl-text-color (#2e2e2e).

• Should make use of new colors defined in variables