Do you mean show ask-line: F8 => common => enable show ask-line?
By "indicators", do you mean the horizontal lines showing the current ask and bid price?
If so, you can turn off the Ask line in the Properties dialog for the chart. There is no UI option for turning off the bid line. However, both can be disabled through code:
ChartSetInteger(0, CHART_SHOW_ASK_LINE, 0);
ChartSetInteger(0, CHART_SHOW_BID_LINE, 0);
The complication is that - no doubt related to the absence of a UI setting - the change to the bid line is not permanent, and is not stored as part of the chart details. If you restart MT4, the bid line re-appears. Similarly, if you turn off the bid line and then save that chart as a template, new charts using that template will show the bid line.
In theory, you could also try setting the colour of the line to clrNONE:
ChartSetInteger(0, CHART_COLOR_BID, clrNONE);
However, while this does work with the ask line (CHART_COLOR_ASK), changing the colour of the bid line seems to have no effect whatsoever in MT4.
In essence, this is an area where the functionality exists in MT5; the equivalent settings exist in the MQL4 language (and in the docs); but MT4 has very incomplete actual support for these features.