Rewriting URLs with spaces

I am working on a website that has URLs that have been indexed by search engines etc. Many of these URLs have spaces.

In the first instance I want to redirect the URLs that no longer exist.
Example pics/Red car.php to go to pics/solar-racer.php

This is my rule

RewriteRule ^pics/Red car.php pics/solar-racer.php [L]

Code (markup):

Leaving a space between Red and car gives me:
The server encountered an internal error or misconfiguration and was unable to complete your request.

I've read:
"\ " is a way of expressing spaces in mod rewrite
and
"\s" is a way of matching spaces

I've tried

RewriteRule ^pics/Red\scar.php pics/solar-racer.php [L]

Code (markup):

but this rule doesn't seem to pick up the pics/Red car.php URL at all.

I will look at replacing all spaces with hyphens but need to sort this problem first.
Any help would be appreciated.

 

(not tested)

RewriteRule ^pics/Red( )car.php$ pics/solar-racer.php [L]

Code (markup):