Paint would be the best answer, but if you're looking for something cheap and quick, just swap out the bedding for something warmer. Soft blues and muted greens are great for bedrooms.

Our primary bedroom is all gray; gray walls, gray rug, gray sheets, gray bedspread. I added a quilt I made that has a rusty red tone.

I'd hang verticle mirrors behind the lamps on the side tables.

Add a red throw and/or pillows to the bed for some contrast. Will go with the Union Jack theme, too.

Maybe try adding some accent colors? Maybe try blue or yellow with some artwork, lamps, pillows, blankets, and bedding. Here are a few bedroom designs to help you more.

Traditional Renovation · More Info

Traditional Renovation · More Info

Traditional Renovation · More Info

I've been working with colors for over 20 years. With respect, I totally disagree with adding warm colors to cool colors. Please keep this all cool colors. Here are the cool colors you can use with your gray: icy light green, icy aqua, silver, cool red, chinese blue, royal blue, light true green, emerald green, pine green, purple. Just for context, here are warm colors: off-white, cream, camel, beige, tan, brown, medium warm turquoise, olive green, peach, golden yellow, gold, orange.

I’d replace the art - using the same grays but in deeper tones with a bit of warm coloring.

I would change to colourful artwork over the bed, change up the bedding, different throw rug. Add colour in an easy inexpensive way. Others have made good suggestions, it’s just a matter of shopping and trying a few things.

The most effective way to add color is an accent wall…right behind the bed…walk-in drama..no other changes needed…i always go to natures uplifting colors … pale sky blue…pale sunny yellow…light green from trees and plants …any bedding will go with those colors